What Are Roman Numerals?
An ancient number system that's been counting for over 2,000 years — and still shows up everywhere.
Numbers Made from Letters
Before the number system we use today (0, 1, 2, 3…) spread around the world, the ancient Romans used letters to represent numbers. These are Roman numerals, and they use just seven symbols: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, and M = 1,000. By combining these letters in specific ways, the Romans could write any number.
The Rules
Roman numerals follow two main rules. Addition rule: When a smaller numeral comes after a larger one, you add them together. VI = 5 + 1 = 6. XIII = 10 + 3 = 13. CLXVI = 100 + 50 + 10 + 5 + 1 = 166.
Subtraction rule: When a smaller numeral comes before a larger one, you subtract the smaller from the larger. IV = 5 − 1 = 4. IX = 10 − 1 = 9. XL = 50 − 10 = 40. CD = 500 − 100 = 400. This subtraction rule keeps numbers shorter — 4 is IV instead of IIII.
Reading Bigger Numbers
With these rules, you can decode any Roman numeral by working left to right. Take MCMXCIV: M = 1,000. CM = 900 (1,000 − 100). XC = 90 (100 − 10). IV = 4. Add them: 1,000 + 900 + 90 + 4 = 1,994. The current year (2026) in Roman numerals is MMXXVI: 1,000 + 1,000 + 10 + 10 + 5 + 1.
Where You See Roman Numerals Today
Roman numerals are everywhere, even 2,000 years after the Roman Empire. Clock faces often use them (the 4 on most clock faces is written IIII rather than IV — a tradition dating back centuries). Super Bowl numbers use them (Super Bowl LVIII = 58). Movie sequels, book chapters, outlines, and building cornerstones frequently use Roman numerals. The copyright year in movie credits is almost always in Roman numerals — watch for it next time the credits roll.
Why We Switched to Arabic Numerals
Our modern number system (called Hindu-Arabic numerals) replaced Roman numerals for everyday math because it includes something Roman numerals lack: zero and place value. Try multiplying XLII by XVII on paper — it's nearly impossible. With Arabic numerals (42 × 17), it's straightforward. The positional system makes arithmetic, algebra, and all higher math dramatically easier.
There's no standard Roman numeral for zero — the Romans didn't have a concept of zero as a number. They used the Latin word "nulla" (meaning nothing) when they needed to indicate an empty value. This lack of zero made advanced mathematics very difficult with Roman numerals, which is one of the key reasons the Hindu-Arabic system (which includes zero) eventually replaced them for calculations worldwide.
Last reviewed: April 2026