Historical calculators

Historical calculators: 6 free calculators & tools, including Roman units and Egyptian cubits. Explore formulas, examples and visual explanations.

Dates & calendars

Convert the same civil day between explicitly selected Julian and Gregorian calendars.

Convert numbers 1–3,999 and standard subtractive Roman numerals in either direction.

Convert Roman length units with an explicitly selected 296 mm foot reference.

Convert royal and common cubits, palms, and digits using a named archaeological reference.

Convert lengths using the Doric foot profile studied at Makyneia in western Greece.

Convert rods, chains, furlongs, and other English lengths using a modern SI yard reference.