Calculate

Percentages, dates, statistics, ratios and other everyday calculations. The tool page shows the formula or the limits that matter for the result.

136 tools in this category.

• Percentage

  Find a percentage of a number, with the formula shown. Example: 15% of 760 = 114.

• Percentage change

  Compare an original value with a new value. An original value of zero is rejected.

• Age at a date

  Completed calendar years and total days between birth and a selected date. Leap-day anniversaries use 1 March in non-leap years.

• Discount

  Calculate the final price and amount saved from a user-entered discount.

• Split a bill

  Split a bill evenly, including an optional tip. No payment is processed.

• Statistics

  Mean, median, repeated modes, range and population/sample variance. Separate numbers with spaces or new lines.

• Scientific calculator

  Evaluate bounded arithmetic expressions without executing code. Supports powers, roots, logarithms and trigonometry in radians.

• Fractions

  Exact fraction arithmetic with integers up to 30 digits and automatic simplification.

• Ratios

  Simplify an integer ratio and scale its components by a chosen factor.

• Geometry

  Areas for rectangles, triangles and circles; volumes for spheres and cylinders. Use consistent length units.

• Trip fuel cost

  Estimate litres and total fuel cost from distance, consumption and a price you supply.

• Weighted average

  Calculate a weighted mean. Provide one non-negative weight for each value; weights must not all be zero.

• Recipe scaler

  Scale ingredient quantities while leaving names and units intact. This is arithmetic, not nutrition or dietary advice.

• Add / remove tax

  Calculate a user-entered percentage tax. No tax law or jurisdiction-specific rate is assumed.

• Simple interest

  Arithmetic projection of principal × rate × years, excluding tax, fees and inflation. Not a prediction or financial advice.

• Compound interest

  Fixed-rate mathematical scenario. Shows principal, growth and final amount. No guarantee of investment returns.

• Fixed payment calculator

  Fixed-rate amortization, monthly interest and principal schedule. Excludes fees, taxes and lender-specific conventions.

• Time / distance conversion

  Converts a supplied elapsed time and distance into minutes per kilometre and average speed. No training targets or health recommendations.

• Weighted grade scenario

  Weighted average and required remaining score under your own percentage-based rules. Does not claim any school’s official grading policy.

• Bezier measure

  Samples a cubic Bezier curve and estimates its length.

• Polygon triangulation

  Triangulates a simple polygon with a local algorithm.

• Delaunay mesh

  Builds a small Delaunay triangulation for entered points.

• Voronoi cells

  Builds Voronoi cells clipped to a local box.

• Linear regression

  Fit y = a + b x to pasted numeric pairs and report residual diagnostics.

• Reliability estimate

  Estimate exponential reliability from failure times with mean time to failure and survival at a chosen time.

• Time series forecast

  Forecast a numeric series with a moving average and report one-step validation error.

• Change point

  Find the single split in a numeric series that minimizes within-segment squared error.

• Time series features

  Extract simple numeric features from a local time series: trend, variance and lag-1 autocorrelation.

• Signal motif finder

  Find repeated numeric windows in a small signal by nearest Euclidean distance.

• 1D Kalman smoother

  Smooth a one-dimensional measurement series with a bounded constant-state Kalman filter.

• Curve fit

  Fit linear, exponential or power curves to pasted x,y points and report R squared.

• M/M/1 queue simulation

  Run a seeded discrete-event simulation for one service queue with exponential arrivals and service times.

• Educational orbit

  Simulate a small two-body orbit in 2D using velocity-Verlet steps and normalized units.

• Solar generation estimate

  Estimate PV energy from area, irradiance, efficiency, performance ratio and sun hours.

• Wind turbine estimate

  Estimate turbine energy from wind speed, rotor diameter, air density, Cp and hours.

• Finite constraint solver

  Brute-force small integer constraints with transparent bounds.

• Tandoor recipes

  Recipe book with meal plan, serving scale and combined shopping list.

• OpenBudgeteer envelopes

  Envelope budgeting: accounts, envelopes, transactions and rollovers without financial advice.

• Optimal transport

  Compares two distributions: exact Wasserstein distance in 1D or a Sinkhorn transport plan in 2D.

• Wavelet transform

  Multi-level discrete wavelet decomposition with reconstruction: Haar and Daubechies-2, per-level energy and a reconstruction accuracy check.

• Sparse dynamics discovery

  Finds governing equations from time series: a polynomial term library and thresholded sparse regression.

• MCMC diagnostics

  Computes per-parameter mean, standard deviation, HDI, R-hat and effective sample size.

• Spatial autocorrelation

  Computes Moran's I and local values for a value grid with rook or queen weights and a permutation p-value.

• Anomaly detection

  Isolation forest: scores how much each point differs from the rest and flags anomalies above a threshold.

• Label noise

  Confident learning: calibrates probabilities per class, estimates the share of wrong labels and lists the most suspicious rows with a label quality score.

• Causal effect

  Estimates the average treatment effect by standardising over confounders, compares it with the naive difference in means and reports the bias and stratum overlap.

• Sobol sensitivity

  Computes first-order and total sensitivity indices with the Saltelli estimator from model outputs on the A, B and AB matrices.

• Quadrature and polynomial chaos

  Builds Gauss-Legendre and Gauss-Hermite nodes and weights, and computes the mean, variance and moments of a polynomial from its expansion coefficients.

• Segregation model

  Schelling agent-based model: agents unhappy with the share of same-type neighbours move until the mean similarity rises.

• Topological data analysis

  Persistent homology of the Vietoris-Rips complex: birth-death pairs, Betti numbers and total persistence for a point cloud.

• Graph analysis

  Builds a graph from an edge list and computes components, density, degrees, betweenness, PageRank, the shortest path and a topological order.

• Study analysis

  From a trial history it computes parameter importance as the share of explained variance and suggests the next point with a TPE density ratio.

• p-median location

  Solves the p-median problem: picks p facilities minimising the weighted sum of distances for weighted demand points.

• Genetic algorithm

  Maximises a polynomial on an interval: tournament selection, blend crossover, Gaussian mutation and elitism, reproducible from a seed.

• Bayesian sampling

  Metropolis-Hastings sampler for the mean of a normal model: posterior mean, interval, acceptance rate and effective sample size.

• Classification and clustering

  Trains a k-nearest-neighbour classifier on a table with accuracy, recall, F1 and a confusion matrix, or runs k-means with its own initialisation and reports inertia.

• Dataset statistics

  Analyses a COCO-style dataset: image and annotation counts, category distribution, imbalance, box areas, out-of-bounds boxes, duplicates and images without annotations.

• Survey logic

  Validates a questionnaire with relevance conditions: unknown variables, duplicate codes, forward references, then computes which questions are visible, skipped and missing for a given response.

• Linear programming

  Solves a linear program with the two-phase simplex method: maximise or minimise a linear objective under linear constraints, reporting the vertex, variable values and constraint slacks.

• Assignment and scheduling

  Solves the assignment problem with the Hungarian method and picks the largest set of compatible intervals with the earliest-finish greedy algorithm.

• Differential equation solver

  Solves y′ = f(x, y) with fourth-order Runge-Kutta or the adaptive Dormand-Prince method, supporting common functions and an optional comparison with the analytic solution.

• 1D finite elements

  Solves the one-dimensional Poisson problem −u″ = f with linear finite elements and Dirichlet boundary conditions, comparing nodal values with the analytic solution.

• Quantum circuit simulator

  Simulates the state of a quantum circuit up to eight qubits: Hadamard, Pauli, phase and rotation gates, CNOT, CZ and SWAP, with amplitudes, probabilities and seeded measurements.

• Astronomy calculations

  Julian date, sidereal time, angular separation between coordinates, airmass with two models, Wien peak and parallax distance.

• Raster grid and windows

  Affine coordinate transform, raster bounds, a window from geographic bounds, pixel ↔ world conversion and resampling with nearest neighbour or bilinear interpolation.

• Raster algebra

  Evaluates an expression over several bands (for example a vegetation index) and reports per-band statistics, a histogram, the median and threshold counts, with NoData support.

• Vector geometry

  Parses WKT (POINT, LINESTRING, POLYGON, MULTIPOLYGON) and computes area, centroid, bounds, length, point membership, distance to the boundary, Douglas-Peucker simplification and box clipping.

• Raster tiles

  Splits a raster into tiles of a given size, reports per-tile statistics and, when a second raster is given, finds changed tiles above a threshold.

• Spectral indices

  Computes NDVI, NDWI, NDBI, GNDVI, SAVI and EVI from band measurements, supports a custom expression and stretches a raster to 0…255.

• Terrain analysis

  From a digital elevation model it computes slope and aspect with Horn’s method, a hillshade, D8 flow direction and flow accumulation.

• Hückel molecular orbitals

  Builds the Hückel matrix from a bond list, finds eigenvalues and orbitals, and computes occupancies, total π energy, the HOMO–LUMO gap, bond orders and atomic charges.

• Crystal structure

  Computes lattice vectors from cell parameters, the cell volume, fractional ↔ Cartesian conversion, minimum-image distances, density and coordination numbers.

• Powder diffraction pattern

  For a cubic structure it computes d-spacings, Bragg angles, structure factors with systematic absences, multiplicities and relative intensities.

• Lattice dynamics

  Computes the phonon dispersion of a one-dimensional chain: acoustic and optical branches for two masses, limiting frequencies at the zone centre and boundary, and a density of states.

• Trajectory analysis

  Reads frames of atomic coordinates and computes quaternion-superposed RMSD, direct RMSD, radius of gyration, per-atom fluctuations, distances and a dihedral angle.

• Two-level system dynamics

  Computes Rabi oscillations for a detuned two-level system: the matrix exponential, excited-state probability, Bloch vector, π-pulse time and a phenomenological decay.

• Zonal raster statistics

  Reclassifies a raster by break values, summarises statistics per zone, builds a distance raster to the nearest source and computes cell visibility from an observer point.

• Street network metrics

  From a node and edge list it computes the total length, edge circuity, mean degree, the number of intersections and dead ends, connected components and the shortest path between two nodes.

• Route planner

  From a distance matrix it builds a nearest-neighbour tour, improves it with 2-opt and compares it with the exact optimum, computes distances from a point and a reachability zone for a time budget.

• Solar position

  Computes solar declination, the equation of time, hour angle, zenith, altitude, azimuth, daylight length and air mass for a given day, latitude and hour.

• Aperture photometry

  Finds the source centroid, computes the aperture sum, background annulus median and scatter, net flux, FWHM and the curve of growth.

• Spectral line analysis

  Estimates the continuum with a median filter, computes the equivalent width, line flux and fits a Gaussian profile with centre, width and depth.

• Kepler orbit

  Solves Kepler’s equation and computes the period, perihelion, aphelion, vis-viva speed, total energy and a table of orbit samples, then checks energy conservation with a numerical integration.

• Lagrangian dynamics

  Integrates the pendulum equations of motion with Runge-Kutta, computes the exact period through the elliptic integral, compares it with the small-angle approximation, tracks energy conservation and checks a harmonic oscillator against its analytic solution.

• One-dimensional diffusion

  Computes the steady temperature profile with a source, runs the transient process with an explicit scheme and an implicit scheme with the Thomas algorithm, and compares them with each other and with the analytic mode decay.

• Solar panel yield

  Computes the angle of incidence on a tilted plane, the plane-of-array irradiance from sky and ground, the cell temperature and power with a temperature coefficient, plus daily energy from an hourly profile.

• Power dispatch

  Orders generators by marginal cost, covers demand within capacity limits, computes cost, emissions and unserved energy, and solves a DC power flow with a slack bus.

• Network load flow

  Computes the voltage drop on a feeder with active and reactive load, the power losses and line loading, plus angles and flows in a DC network with a slack bus.

• Robot kinematics

  Builds the transform from a Denavit-Hartenberg table, computes the gripper position, solves the inverse problem for a two-link planar arm on both branches and checks the Jacobian determinant.

• Wind turbine power

  Converts wind speed to hub height with the power and log laws, computes air density, interpolates the power curve, averages power over a Weibull distribution and reports the capacity factor and annual energy.

• Pipe flow

  Computes the Reynolds number, the friction factor from the laminar law and the Colebrook equation, Darcy-Weisbach head loss, pressure drop and the combined loss of series pipes.

• Building thermal load

  Computes heating and cooling degree days from a temperature series, the balance temperature with internal and solar gains, the peak conduction loss and the annual heating and cooling energy.

• Stormwater runoff

  Computes the peak flow by the rational method, the Kirpich time of concentration, the full-pipe Manning capacity, the runoff volume and level-pool storage routing.

• Reservoir water balance

  Simulates the monthly reservoir balance with inflow, demand, environmental release and spill, and reports volume and time reliability plus the total deficit.

• Lifecycle impact assessment

  Multiplies an emission inventory by characterisation factors (GWP100 for AR4, AR5 or AR6) and reports the total impact in kg CO2-eq with per-flow contributions and shares.

• Carbon footprint

  Turns everyday activities into emissions with standard factors, computes the footprint per person and per unit of GDP, the years left in a carbon budget and the annual reduction needed to reach a target year.

• Climate indices

  Computes ETCCDI daily climate indices from a series of minimum and maximum temperatures and precipitation: frost, ice and summer days, tropical nights, growing degree days, daily range, longest warm and dry spells, precipitation intensity and total.

• Labelled array

  Reads a data cube as a stack of grids over time and computes the time and space mean, the area weighted mean (cosine of latitude), anomalies against a baseline period, the standard deviation and block coarsening.

• Water network

  Solves the minimum cost allocation of water from sources to demands with supply, demand and capacity limits, shows the links used and the pipe head loss.

• Water occurrence

  From a stack of water masks it computes the water occurrence per cell, classifies cells as permanent, seasonal or never flooded, finds lost and new areas and estimates their extent.

• Shared task board

  A multi-user task board on the local server: accounts, workspaces, four permission-checked roles, status columns, assignees, comments, votes, version history and an activity feed. Several people work on one board at the same time.

• Shared wiki with versions

  A shared wiki on the local server: pages with versions, editor and reader roles, comments, edit history and an activity feed inside a workspace.

• Polls and voting

  Shared polls on the local server: answer options, one vote per member, vote counting, leader and tie detection, changing or withdrawing a vote, comments.

• Feedback board

  A shared suggestion board on the local server: submitting ideas, up and down votes, ranking by score, accepted, planned and declined states, comments.

• Shared pastes with expiry

  A shared text-paste store on the local server: pastes with an expiry, comments and version history inside a workspace with permission checks.

• Workspace notifications

  A workspace event feed on the local server: who created, changed, commented, voted or added a member, with targets and times; members share the same history.

• Read-later list

  A shared read-later list on the local server: links with descriptions, tags, unread and read states, comments and full-text search across titles, descriptions and tags inside a workspace.

• Shared feeds and entries

  Shared feeds on the local server: feeds and feed entries, unread counts per feed, read marks, stars, tags, comments and search inside a workspace.

• Link archive with snapshots

  A shared link archive on the local server: a snapshot with its link, capture time, content type and size, protection against adding the same link twice, tags, comments and archive search.

• Shared file browser

  Shared files on the local server: file records with a path, size in bytes and text content, tags, comments, versions and search by name, path and content inside a workspace.

• Local workspace search

  Search on the local server across workspace items: every query word must appear, results are ranked by the number of matches, snippets are shown, with filters by kind, status and tags over titles, descriptions and tags.

• Location history

  Computation from your own points in the browser: total great-circle distance, speed, longest leg, distance from home, per-day breakdown, most visited places with time spent, bounding box and centroid; everything is computed locally without maps or external services.

• Propositional logic prover

  A local prover for propositional logic: parses formulas with not, and, or, if-then, if-and-only-if, builds the full truth table, decides tautology, contradiction and satisfiability, reports a counterexample, converts the negation to conjunctive form and runs resolution until it derives the empty clause.

• Notebook with cells

  A local notebook in the browser: one cell per line, variable definitions visible to later cells, evaluation of arithmetic and logical expressions, a per-cell error report, a results table and the final variables.

• Shared newsletters and subscribers

  Shared newsletters on the local server: a subscriber list with tags, campaigns with a subject and body, substitution of subscriber fields into the text, recipient counting, draft, ready and sent states, comments and search. Nothing is actually sent.

• Shared code snippets

  A shared snippet store on the local server: a snippet with its language in the metadata, tags, edit versions, comments, search by content and tags, and a per-day breakdown.

• Shared library

  A shared library on the local server: a book with author, series and year in the metadata, tags, unread, reading and finished states, comments, versions and search by title, author and tags.

• Contacts and calendar in standard formats

  Local parsing and production of standard formats: reading vCard 4.0 and iCalendar, unfolding folded lines, parsing property parameters, escaping and unescaping text, folding long lines at 75 characters, normalized output and a check that the output parses back.

• Direct current circuit solver

  A local direct current solver using nodal analysis: resistors, voltage and current sources, node voltages, element currents and powers, a Kirchhoff check at every node and a power balance.

• Digital logic and truth tables

  A local digital circuit engine: and, or, not, nand, nor, xor gates, buffers, inputs, outputs and flip-flops; settling to a stable state with oscillation detection, a full truth table for combinational circuits and step-by-step progress for sequential ones.

• RISC-V (RV32I) simulator

  A local RV32I simulator: its own assembler with labels and pseudo-instructions, execution of moves, arithmetic, shifts, comparisons, loads, stores, branches and jumps, memory, an instruction trace, and a report on registers, memory writes and the halt reason.

• Block programs and code generation

  A local block-program engine: setting and changing variables, repeats, loops, conditions with comparisons, printing values, counting executed steps and generating JavaScript and Python code from the same block description.

• Command sketches to SVG

  A local drawing engine: circles, rectangles, lines, polygons, colours, translation, rotation and scaling, repeats of command groups; computes the bounding box, line length and area and produces a ready SVG file.

• Interval, scale and chord reference

  A local music theory reference: fourteen scales with correct degree spelling (including E# in F sharp major and Bb in B flat major), nineteen chords from triads to ninth chords, interval names and symbols including compound and descending cases, and transposition of a note list with chromatic spelling.

• Chord and harmony analysis of a score

  A local harmony analysis: parses a chord progression, identifies each chord from its pitch classes including inversions, detects the key by correlating with the Krumhansl-Schmuckler profiles, writes roman numerals with degree quality and function, and recognises cadences.

• Tempo and beats of your own audio

  A local tempo estimate: a spectral flux envelope, autocorrelation with parabolic interpolation, beat picking with a threshold and a refractory gap, and a period refined by least squares over the detected beats.

• Audio features for analysis

  Local feature extraction: RMS, zero-crossing rate, spectral centroid, 85% energy rolloff, spectral flatness, spectral flux and thirteen mel-frequency cepstral coefficients from an own DFT, mel filter bank and DCT-II.

• Pitch detection and tuner

  A local pitch detector: autocorrelation with a first-significant-peak rule so the octave below is not reported, parabolic lag interpolation, the nearest note with its octave, the deviation in cents from equal temperament and a confidence value.

• Change tempo without changing pitch

  Local overlap-add audio processing with a Hann window: time stretching that keeps the pitch, pitch shifting by a number of semitones through stretching and resampling, pitch measurement before and after the change and a downloadable result.

• Noise suppression in your own recording

  Local spectral subtraction: a short-time Fourier transform with a Hann window, a noise profile taken from the start of the recording, a power-domain Wiener gain that keeps the phase, zero padding for exact reconstruction, and honest measurements of the residual noise and of the match with the clean signal.

• Repeating CSS pattern generator

  A local CSS pattern generator from a description: dots, squares, triangles, stripes, checkerboard and crosses, a grid from 1×1 to 12×12, up to six colours, gaps, rotation, stripe angle and opacity; the output contains ready CSS with layer, size and position lists, a .css file and an SVG preview of the same grid.

• Interface micro-animations from a description

  A local animation generator: a list of name, property, start and end value, duration and easing; the output contains ready @keyframes and classes, a Web Animations API description, a stagger delay between animations, and a check that stops braces and semicolons from being injected into values.

• Generative poster from a seed

  A local poster generator: a deterministic random generator, a grid with jitter, circles, squares, triangles or lines, rotation, a palette of up to eight colours, an ink coverage metric and a ready SVG file. The same seed always produces the same poster.

• Synthesizer and sequencer

  Compose notes, choose a waveform, loop playback and export WAV. Sound starts only on request.

• Scheduled metronome

  Set tempo and beats per bar. Beats are scheduled against the browser audio clock.

• Perception experiment

  Define text stimuli and response keys. Randomized trials, reaction times, accuracy and CSV. Voluntary participation; memory only.