How to explain arithmetic in Roman numerals, rules, order & arithmetic to your child
22 October 2026
Roman numerals use letters instead of digits, so adding them can seem tricky at first. By breaking the process into simple steps, your child can see how the rules and order work in practice.
Worked example
XV + VIII
Step 1: XV is 10 + 5, which is 15. VIII is 5 + 1 + 1 + 1, which is 8.
Step 2: Add the values: 15 + 8 = 23.
Step 3: Write 23 in Roman numerals. 20 is XX, 3 is III. So, 23 is XXIII.
The correct answer is XXIII.
| Roman Numeral | Value |
|---|---|
| XV | 15 |
| VIII | 8 |
| Total | 23 |
| Roman Numeral | XXIII |
After working through this example, your child will recognise how to add Roman numerals by converting, adding, and then writing the answer in Roman numerals. They can now try similar questions to build confidence with this skill.
