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Percentage Calculator
Work out what share one number is of another, take a percentage of a value, or measure the change between two numbers.
Share · change -
Discount Calculator
Apply a percentage discount and a fixed-amount coupon, reverse a sale price back to the original, or stack several discounts step by step.
Final price · coupon · original price -
Date Difference Calculator
Count the days between two dates, with an option to include the first day, plus a breakdown into years, months and days.
Days · years, months, days -
D-day Calculator
See how many days remain until a target date, whether today is the day, or how long ago it passed — with the weekday.
Days left · days since -
Time Calculator
Add up several durations, or measure the gap between two clock times — including shifts that run past midnight.
Add durations · time between -
Unit Converter
Convert length, mass, area and volume between metric and US customary units, including the Korean pyeong for floor area.
Length · mass · area · volume
Every calculation runs in your browser; nothing you type is stored or sent. Each tool shows its formula and worked examples.
These are general-purpose everyday calculators. Do not rely on them for tax, financial-product or medical decisions.