Roman Numeral Decoder
Read a message written in Roman numerals and type the number it means, from the clock numbers I to XII up to M and years like MCMXCIV.
Good to know
The Roman numerals
Roman numerals are letters that stand for numbers. These are the ones to know, and the four that work backwards.
The letters
I 1
V 5
X 10
L 50
C 100
The ones that go backwards
IV 4 one before five
IX 9 one before ten
XL 40 ten before fifty
XC 90 ten before a hundred
Roman numerals to 1000
Year 5 carries the numerals on past a hundred. Two more letters, and two more pairs that go backwards.
The letters
I 1
V 5
X 10
L 50
C 100
D 500
M 1000
The ones that go backwards
IV 4 one before five
IX 9 one before ten
XL 40 ten before fifty
XC 90 ten before a hundred
CD 400 a hundred before five hundred
CM 900 a hundred before a thousand
More Roman numerals practice
For grown-ups
Roman numerals are letters that stand for numbers: I is 1, V is 5, X is 10, L is 50, C is 100, D is 500 and M is 1,000. Children meet I to XII on clock faces in Year 3, read numerals up to C (100) in Year 4, and up to M (1,000) in Year 5, including years.
What the game does
- Each go is eight messages, each written in Roman numerals on an old card, and your child types the number it means on the keypad.
- Most messages have a smaller letter in front of a bigger one, like the IV in 14 or the XC in 90, because that is where children slip: they add every letter and read IV as 6.
- A Hint button marks the card up in pencil: first it splits the numeral into the parts to read, then it writes what each part is worth. If your child is still stuck after both, the game tells them the number to type.
- Roman numerals have no zero: 40 is just XL. That is a good moment to talk about why our numbers need one.
- Each message is worth 3 stars, and a hint or a wrong try costs one. There is no timer and no pass or fail, and nothing is saved: close the page and it is gone.
How to help at home
- Spot Roman numerals out and about: on clock faces, at the end of a film's credits, in a king's or queen's name like Henry VIII, and on chapter numbers.
- Read long ones in parts, biggest first: MMXXVI is MM, then XX, then VI, so 2,000, 20 and 6.
- Ask your child to write their age, or this year, in Roman numerals.