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How to Read and Write Roman Numerals
The seven Roman numeral symbols, the add-and-subtract rules that combine them, and why there's no zero — with a converter that goes both ways from 1 to 3,999.
Updated 26 October 2026 · 2 min read
Roman numerals still turn up on clock faces, book chapters, film copyright dates and Super Bowl titles. The whole system rests on just seven letters, each standing for a fixed value, combined by a couple of simple rules.
The seven symbols
Every Roman numeral is built from these. There's no symbol for zero and no place value in the way our decimal system has — the position of a letter changes its meaning only through the add-and-subtract rules below.
The add-and-subtract rules
- Add when symbols don't get larger left to right. VI is 5 + 1 = 6; XV is 10 + 5 = 15; MCC is 1,000 + 100 + 100 = 1,200.
- Subtract when a smaller symbol sits before a larger one. IV is 5 − 1 = 4; IX is 10 − 1 = 9; XL is 50 − 10 = 40; CM is 1,000 − 100 = 900.
- Never repeat a symbol more than three times in a row. You write 4 as IV, not IIII, and 40 as XL, not XXXX.
Only certain subtractions are allowed: I can precede V and X; X can precede L and C; C can precede D and M. That's why 99 is XCIX (90 + 9), not IC. Working from the largest value down and applying these rules in order is the reliable way to build any numeral — and exactly what the Roman numeral converter does automatically, in either direction.
Reading a numeral back into a number
Scan left to right. Add each symbol's value, but if a symbol is smaller than the one immediately after it, subtract it instead. Take MMXXVI: M (1,000) + M (1,000) + X (10) + X (10) + V (5) + I (1) = 2,026. Or MCMLXXXIV: 1,000 + (1,000 − 100) + 50 + 30 + (5 − 1) = 1,984.
Why the limit is 3,999
With M as the largest everyday symbol and no symbol repeated more than three times, the biggest number you can write in the standard system is MMMCMXCIX — 3,999. Larger values historically used a bar over a numeral to multiply it by a thousand, but that notation is rarely needed today, so most converters, including ours, cover 1 to 3,999.
Where you'll still meet them
- Clock and watch faces, where 4 is sometimes shown as the older IIII.
- Book chapters, outlines and appendix numbering.
- Copyright and release years on films and TV programmes.
- Monarch and pope names — Elizabeth II, Louis XIV.
Roman numerals are really just a different way of writing the same quantities we count in every day. If you enjoy number systems, our guide to square roots and the percentages explainer are good companions for brushing up on the maths behind the symbols.
Frequently asked questions
- Why is there no zero in Roman numerals?
- The Roman system was built for counting and tallying, where a symbol for 'nothing' wasn't needed, and it has no place-value column that a zero would hold open. The concept of zero reached Europe later, through the Hindu-Arabic numerals we use today.
- Is 4 written IV or IIII?
- The standard modern form is IV, using the subtraction rule. The older additive form IIII still appears on many clock faces by tradition, but for everyday writing IV is correct.
- How do I write large numbers like 2026?
- Break it into thousands, hundreds, tens and units and convert each: 2026 = 2000 (MM) + 20 (XX) + 6 (VI) = MMXXVI. A converter does this instantly and also reads numerals back into numbers.