Everyday calculators

Percentages, dates, averages and time differences, worked out in seconds with the steps shown.

How much a value went up or down

Map growth over time

Statistical calculations

Great-circle distance worldwide

Days, months & years between dates

Years, months & days between dates

Convert numbers to and from Roman

How far to sit from your screen

Coffee-to-water ratio by method

% of, is what % of & % change

Mean, variance & spread of data

Box, cylinder, sphere, cone & pyramid

Bedtime & wake-up by sleep cycles

Weekday for any date