🧮 Calculators
Calculators that show their working. Every financial tool states its formula and its assumptions, because a number without either is impossible to check.
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About calculators
The problem with most online calculators is not the arithmetic — it is the hidden assumptions. A loan calculator that omits how it compounds, or a salary converter that quietly assumes 52 paid weeks, produces a plausible number that does not match reality.
These tools show the formula alongside the result, list what is excluded, and flag the situations where the answer stops being reliable. The financial ones say plainly that lenders and tax authorities apply their own rounding and fees, so treat the output as a well-specified estimate rather than a quote.
The date and time calculators handle the awkward cases explicitly: leap years, month-end arithmetic, daylight saving transitions and the difference between inclusive and exclusive day counting.
Most used in this category
Work out an exact age in years, months and days.
Five percentage calculations in one place, with the working shown.
Full mortgage payment with tax, insurance and deposit.
Monthly payment, total interest and full amortisation schedule.
Other categories
Merge, split, compress, rotate and convert PDF documents.
Convert, compress, resize, crop and rotate images.
Format, validate, encode and test — JSON, Base64, regex and more.
Count, convert, sort, deduplicate and compare text.
Length, weight, temperature, speed, storage, time zones and number bases.
Passwords, hashes, UUIDs and random numbers.