30 subjects · 2,548 calculators

All calculators

Every calculator here is a formula, not a lookup table. The inputs feed exact rational arithmetic, the working is printed underneath, and where a figure comes from a measurement rather than a definition the page says so.

A–Z index

Health & fitness

Body composition, energy needs, training load and dosing, each with the formula it actually uses named rather than hidden.

Money & finance

Loans, savings, interest, tax and investment arithmetic, computed in exact fractions so a 360-payment schedule does not drift a cent.

Mathematics

Algebra, number theory, fractions, bases and the rest of the school and university toolkit, at arbitrary precision.

Geometry

Area, perimeter, volume and surface area for every shape you are likely to meet, plus triangle and circle solvers.

Statistics & probability

Descriptive statistics, distributions, sample sizes, confidence intervals and combinatorics.

Physics

Mechanics, waves, thermodynamics, optics and relativity, with SI defining constants used at their exact values.

Chemistry

Molar mass, solutions, gas laws and stoichiometry. Molar masses are computed from IUPAC atomic weights, never transcribed.

Electrical

Ohm law, power, wiring, voltage drop, motors, batteries and solar, in both AWG and metric conductor sizes.

Construction & DIY

Concrete, framing, roofing, flooring, paint and landscaping quantities, with waste allowances made explicit.

Material weight

What a bar, sheet, tube or block of a given material weighs, from its dimensions and its density.

Machining & metalwork

Speeds and feeds, tap drills, thread engagement, sheet metal gauges, bend allowance and press tonnage.

Automotive

Gearing, tyre sizes, engine geometry, performance estimates and running costs.

Computing & networking

Subnets, transfer times, storage, encoding bitrates and display geometry, keeping decimal and binary prefixes apart.

Cooking & baking

Ingredient weights, tin sizes, recipe scaling, oven temperatures and baker percentages.

Brewing & fermentation

Gravity, alcohol, bitterness, priming, dilution and mash arithmetic for beer, wine, cider and mead.

Energy & environment

Solar arrays, battery banks, heat pumps, running costs, carbon and water footprints.

HVAC & plumbing

Heating and cooling loads, duct and pipe sizing, flow, pressure drop and water heating.

Sensors & control

Instrumentation scaling, PID tuning, signal conditioning and loop arithmetic.

Photography & video

Depth of field, exposure, field of view, time-lapse and file-size arithmetic.

Audio & music

Decibels, impedance, delay and reverb times, room modes, tuning and sample-rate arithmetic.

Astronomy & space

Orbits, weights on other worlds, telescope optics, light travel time and rocket performance.

Aviation & marine

Density altitude, true airspeed, crosswind, weight and balance, great-circle routes and sailing arithmetic.

Sports & training

Pace, splits, power, scoring and rating systems across running, cycling, swimming and field sports.

Farming & garden

Fertiliser, seeding, spraying, irrigation, feed, yield and soil arithmetic per hectare or per acre.

Pools & aquariums

Water volume, dosing, turnover, heating and salinity for swimming pools, ponds and fish tanks.

Textiles & crafts

Yarn, fabric, quilting, resin, candles, soap and 3D-printing quantities.

Business & marketing

Margin, markup, break-even, unit economics, advertising and conversion arithmetic.

Games & odds

Dice, cards, lotteries, betting odds, drop rates and rating systems, worked exactly.

Time & date

Ages, durations, working days, shift patterns, countdowns and calendar arithmetic.

Everyday

Percentages, tips, splits, discounts, fuel costs and the small arithmetic of ordinary life.