Calculators tools

Work out percentages, dates and conversions.

Average speed calculator

Calculate average speed in km/h, m/s and mph from distance and elapsed time.

Weighted average calculator

Calculate an average when values have different weights, such as grades or quantities.

Rule of three calculator

Solve direct or inverse proportions and see the formula used.

Mean, median and sum

Calculate the mean, median, sum, minimum and maximum of a number list.

Percentage calculator

Calculate the amount represented by a percentage of a value.

Percentage change

Calculate the relative increase or decrease between two values.

Days between dates

Count the calendar days separating two dates.

Add or subtract days

Find the date after adding or subtracting calendar days.

Unit converter

Convert length, mass, temperature, area, volume and speed.

Unix timestamp converter

Convert Unix seconds or milliseconds to UTC dates and back.

Aspect ratio and proportions

Calculate an aspect ratio and the height for a new width.

Choose the formula before entering values

Identify units and the calculation’s base. Numeric fields accept a comma or period as the decimal separator; avoid thousands separators so that 1,000 is not interpreted as 1.

Find a portion

Calculates a percentage of an amount. Subtract the calculated portion for a discounted price.

Percentage calculator →

Compare two values

Uses the initial value as the base. Returning to the original price can require a different percentage from the discount.

Percentage change →

Scale quantities

Choose direct when ratios stay constant and inverse when products stay constant. Check the problem’s conditions.

Rule of three calculator →

Summarize a series

Compare mean and median. Separate numbers with spaces, newlines or semicolons.

Mean, median and sum →

Date calculations count calendar days. Proportions need consistent units and a nonzero denominator. Displayed results may be rounded.

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