Ross MackellUK-qualified primary teacher · 7 min read

Ask your child to write 49 in Roman numerals. A lot of children write IL. Some write XXXXVIIII. The answer is XLIX, and once your child sees why, Roman numerals stop being a puzzle and become a pattern.

Roman numerals turn up on clock faces, at the end of films, on buildings and in Year 4 and Year 5 maths lessons. They also turn up in the Year 6 SATs reasoning papers. The good news is that there are only seven letters to learn and two rules to remember.

I'm Ross, a UK-qualified primary teacher with over ten years in the classroom. In this guide I'll explain the seven Roman numerals, the add and subtract rules, how to convert in both directions, how to write years, how they come up in SATs, the mistakes I see most often, and practice questions with answers.

What your child needs first

Roman numerals are built on two things your child will already be using:

• Place value. To write 384 in Roman numerals, your child needs to see it as 300 + 80 + 4. If that step is shaky, start with what is place value.
• Partitioning and simple adding. Reading CCLXIII means adding 100 + 100 + 50 + 10 + 1 + 1 + 1. Children who are confident with partitioning find this quick.

In the national curriculum, children read clock faces with Roman numerals from I to XII in Year 3. In Year 4 they read Roman numerals to 100 and learn that our number system changed over time to include zero and place value. In Year 5 they read Roman numerals to 1000 (M) and recognise years written in Roman numerals.

The seven Roman numerals

Everything is built from these seven letters. Learn them first, before any rules:

A silly sentence helps lots of children remember the order: I Value Xylophones Like Cows Do Milk. I, V, X, L, C, D, M, from smallest to biggest.

The two rules

Rule 1: add. When letters are the same size or get smaller from left to right, add them up. VI = 5 + 1 = 6. XXV = 10 + 10 + 5 = 25. CLX = 100 + 50 + 10 = 160.

Rule 2: subtract. When a smaller letter comes just before a bigger one, take it away. IV = 5 − 1 = 4. XC = 100 − 10 = 90.

There are only six subtraction pairs, and it's worth learning them as a set:

Notice the pattern: you only ever subtract I, X or C, and only from the next two letters up. That's why 49 can't be IL. I can only come before V or X.

One more thing: you never use the same letter more than three times in a row. 4 is IV, not IIII. (Some clock faces do use IIII for 4. That's a clockmakers' tradition, not the rule your child will be marked on.)

Reading Roman numerals

To turn Roman numerals into a number, read from left to right. Spot any subtraction pairs first, then add everything up.

Example 1: XVII

1. No smaller letter comes before a bigger one, so just add.
2. X + V + I + I = 10 + 5 + 1 + 1.
3. The answer is 17.

Example 2: XIV

1. Spot the subtraction pair: IV (I is before V). That's 4.
2. Now add: X + IV = 10 + 4.
3. The answer is 14, not 16.

Example 3: MMXXVI (a year)

1. No subtraction pairs. Group the letters: MM, XX, VI.
2. MM = 2000, XX = 20, VI = 6.
3. The answer is 2026.

A good habit is to draw a little bracket under each subtraction pair before adding anything. It stops your child adding the I in XIV.

Writing numbers as Roman numerals

This is the direction children find harder. The trick is to never try to do the whole number at once.

Example 4: 49

1. Split it: 49 = 40 + 9.
2. 40 is XL (10 before 50).
3. 9 is IX (1 before 10).
4. Join them: XLIX.

Example 5: 384

1. Split it: 384 = 300 + 80 + 4.
2. 300 is CCC.
3. 80 is 50 + 30, so LXXX.
4. 4 is IV.
5. Join them: CCCLXXXIV.

Example 6: the year 1999

1. Split it: 1999 = 1000 + 900 + 90 + 9.
2. 1000 is M. 900 is CM. 90 is XC. 9 is IX.
3. Join them: MCMXCIX.

This is also a nice moment to talk about why our number system won. Try working out 384 + 49 in Roman numerals, then with column addition. Place value and zero make our way much quicker, which is exactly the point the Year 4 curriculum wants children to understand.

Roman numerals in SATs

Roman numerals don't appear on the arithmetic paper, but they do come up in the Year 6 SATs reasoning papers. These are the question types to practise:

For more on how the SATs papers are set out, see the guide to the Year 6 SATs arithmetic paper.

5 common mistakes and how to fix them

Mistake 1: Subtracting from too big a letter

Your child writes 49 as IL, or 99 as IC.

The fix: I only goes before V and X. X only goes before L and C. C only goes before D and M. Then use the split method: 99 = 90 + 9 = XC + IX = XCIX.

Mistake 2: Four of the same letter in a row

Your child writes 40 as XXXX or 4 as IIII.

The fix: three in a row is the limit. When they'd need a fourth, it's time for a subtraction pair: XL or IV.

Mistake 3: Adding the subtraction pair

Your child reads XIV as 16.

The fix: bracket every pair where a smaller letter comes before a bigger one, and work those out first. XIV is X + (IV) = 10 + 4.

Mistake 4: Converting digit by digit

Your child writes 49 as IVIX, turning the 4 and the 9 into numerals separately.

The fix: the 4 in 49 is worth 40, not 4. Partition first: 40 + 9. This is a place value mistake in disguise.

Mistake 5: Mixing up L, C and D

Your child reads D as 50 or L as 500.

The fix: go back to the memory sentence and the table. Five minutes of quick-fire flashcards (show a letter, say the value) sorts this out in a few days.

Practice questions

Same three steps I use for every skill: watch, copy, practise. Do the first one out loud yourself, then let your child have a go at a similar one before they try the rest on their own. Cover the last column and ask your child to fill in the gaps.

Bonus question: using I, V and X exactly once each, what's the biggest number you can make? (Answer: XVI, which is 16.)

Ten minutes, a few times a week, is plenty. A fun extra: spot Roman numerals out and about together, on clocks, buildings and film credits, and work out what they say.

Frequently asked questions

What are the Roman numerals from 1 to 10?

The Roman numerals from 1 to 10 are I, II, III, IV, V, VI, VII, VIII, IX and X. Notice that 4 is IV (one before five) and 9 is IX (one before ten).

What is 50 in Roman numerals?

50 in Roman numerals is L. The seven Roman numerals are I (1), V (5), X (10), L (50), C (100), D (500) and M (1000).

How do you write 2026 in Roman numerals?

2026 is MMXXVI. Split it into 2000 + 20 + 6. 2000 is MM, 20 is XX and 6 is VI, so together it is MMXXVI.

Why is there no zero in Roman numerals?

The Roman system does not use place value, so it never needed a symbol for zero. Each letter always has the same value wherever it sits. Our number system uses place value, so zero is needed to hold a place, as in 305.

What year do children learn Roman numerals?

In England, children read clock faces with Roman numerals I to XII in Year 3. In Year 4 they read Roman numerals to 100, and in Year 5 they read Roman numerals to 1000 and recognise years written in Roman numerals.

Sources and further reading

• Department for Education, National curriculum in England: mathematics programmes of study (number and place value, and measurement, Years 3, 4 and 5)
• Standards and Testing Agency, Key stage 2 mathematics test framework
• Ross Mackell, Teacher's Perspective on YouTube