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The everyday helpers: basic calc, percentage, ratio, average, scientific notation, Roman numerals, prime numbers.
Tap any card to open its calculator page.
Calculate percentage of a number, percentage change, percentage difference, and the most common percent-of-total questions.
Standard four-function calculator with percent and sign toggle — just like the one on your phone.
Simplify any ratio to its lowest terms using GCD
Calculate mean, sum, and non-zero count for up to five values
Convert between scientific notation and standard form
Break down any number (1–3999) into its Roman numeral digit components
Check primality, find the nearest prime above, and count prime factors
All 570 calculators in your pocket. Offline-ready, no ads, no trackers. iOS and Android apps land soon — get notified when they ship.