Average calculator
Explore mean, median, modes, range, and standard deviation with a live distribution of your number list.
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Calculators
Calculators that show their work.
Fraction calculator
Add, subtract, multiply, and divide fractions with exact reduced answers and an equal-parts preview.
Number to words
Write exact numbers in English words, with place-value groups and digit-by-digit decimals.
Percentage calculator
Find a percentage, compare a part to a whole, or explore percentage changes with a live equation.
Prime number checker
Check whether an integer is prime and see a divisor or the exact trial-division evidence.
Random number generator
Draw random integers from an inclusive range, choose unique results, and reveal a copyable list.
Ratio calculator
Simplify two ratio parts and scale either side to a target while preserving an exact relationship.
Roman numeral converter
Convert numbers and Roman numerals in either direction, with a breakdown of additive and subtractive symbols.
Scientific calculator
Calculate typed expressions or use the keypad, switch angle modes, and recall your recent calculations.
Unit converter
Convert length, mass, temperature, area, volume, speed, time, and storage with clear units and a quick swap.
Averages, fractions, percentages, ratios, prime checks, random draws, Roman numerals, unit conversion, and a scientific calculator with session history. Results include the equation or evidence behind them.
Calculations use practical precision and state the input ranges and rounding behavior they apply.
Everyday calculations
The percentage calculator covers the three questions people actually ask: what is x% of y, what percentage is x of y, and what is the percentage change from one value to another. The ratio calculator simplifies and scales ratios for recipes, mixtures, and aspect ratios. The fraction calculator gives exact reduced answers, and the average calculator reports mean, median, mode, range, and standard deviation for a list of numbers.
The unit converter handles length, mass, temperature, area, volume, speed, time, and data storage, including the easily confused pairs: US and imperial gallons, statute and nautical miles, decimal and binary gigabytes.
Showing the work
Each calculator shows the equation or evidence behind its answer, not just the number, so you can check it, learn from it, or paste it into a report. The prime checker lists the trial divisions it performed, the Roman numeral converter breaks a numeral into its additive and subtractive parts, and number to words shows each place-value group.
Where exactness matters, the tools use exact integer arithmetic: fractions, ratios, and prime checks. Where they use floating-point arithmetic, results are rounded to 12 significant digits to hide representation noise such as 0.1 + 0.2 = 0.30000000000000004. The random number generator uses the browser's cryptographic random source without modulo bias.