Writing Roman numerals

To turn a number into a Roman numeral, break it into tens and ones, then write the tens part first, then the ones. Stick to a small set of safe rules and you'll get it right every time.

Two-step method

1. Split the number into tens and ones. 47 = 40 + 7.
2. Write the tens part in Roman, then the ones part in Roman, side by side.

That's it. For numbers under 100, the tens and ones never interfere with each other.

The "ones" toolbox (1–9)

The "tens" toolbox (10–90)

Putting them together

That's the whole method.

Safe-writing rules

1. Never use a subtractive pair when a simpler form is allowed. Don't write IIII for 4 — use IV. Don't write VIIII for 9 — use IX.
2. Never write more than three identical letters in a row. III is OK, IIII is not. Same for XXXX (use XL) and CCCC (use CD — but that's beyond Year 4).
3. V, L, D are never doubled. No VV (that would be 10 = X), no LL (that would be 100 = C). Just go to the next symbol.
4. Subtractive pairs use only specific letters. I can be subtracted from V or X. X can be subtracted from L or C. (L cannot be subtracted from anything in Year-4 work.) That means VL for 45 is wrong — the correct form is XLV (40 + 5).

A worked example

Write 76 in Roman numerals.

• Split: 76 = 70 + 6.
• Tens part: 70 = LXX.
• Ones part: 6 = VI.
• Put them together: LXXVI.

Write 94 in Roman numerals.

• Split: 94 = 90 + 4.
• Tens part: 90 = XC (subtractive).
• Ones part: 4 = IV (subtractive).
• Together: XCIV.

What's next

• Worked examples
• Reading Roman numerals
• Back to the introduction

Try it out

• ✍️ Write a Roman numeral
• 🎯 Mixed Roman numerals