Online date and measurement calculators

Compute the greatest common divisor and least common multiple of integers.

Look up ISO week, week year, weekday and day of year for a date.

Add durations in minutes and seconds or hours, minutes and seconds.

Estimate upload or download time from size, speed and efficiency.

Count Monday-to-Friday days and exclude dates you supply.

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

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

Solve direct or inverse proportions and see the formula used.

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

Calculate exact age in years, months and days and the time until the next birthday.

Calculate the monthly payment, total interest and amortization table of a loan.

Add or remove VAT or another tax by percentage and get net, tax and total.

Convert integers from 1 to 3999 to Roman numerals and validate the reverse conversion.

Add, subtract, multiply and divide fractions with exact, simplified results.

Factor integers from 2 to one trillion into primes and check their product.

Convert CSS pixels and rem in either direction using your chosen root font size.

Calculate the final price, savings and equivalent discount for two successive reductions.

Calculate the amount represented by a percentage of a value.

Calculate the relative increase or decrease between two values.

Count the calendar days separating two dates.

Find the date after adding or subtracting calendar days.

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

Convert Unix seconds or milliseconds to UTC dates and back.

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