How to use
- Enter a number (1–3999) on the left or a Roman numeral on the right.
- The counterpart appears instantly, with the breakdown below.
- Use “Current year” to convert this year.
How Roman numerals work
The basic symbols are I = 1, V = 5, X = 10, L = 50, C = 100, D = 500 and M = 1000. They are added, with the largest on the left: XVI = 10 + 5 + 1 = 16.
A smaller symbol before a larger one is subtracted: IV = 4, IX = 9, XL = 40, XC = 90, CD = 400, CM = 900. No more than three identical symbols appear in a row.
Frequently asked questions
Why only up to 3999?
The classic notation has no symbol above M (1000). Larger numbers used overlines, which are rarely used today.
Is there a Roman zero?
No, the Romans had no zero as a number.
Why do clocks show IIII instead of IV?
It's an old tradition for visual balance. By today's rules IV is correct – the tool points out such variants.