Roman Numeral Converter
Convert both ways from 1 to 3999, recognising all four subtractive forms, plus the symbol sum and length.
How to Use
- Enter either form
Auto-detect is the default: plain digits are read as Arabic, anything made of Roman letters as Roman, and you can also force the type.
- Convert both ways
2024 gives MMXXIV, MMXXIV gives 2024, and the round-trip check rejects non-standard forms like IIII.
- Use the extras
The symbol sum and character count come along for free, ready for inscription analysis or puzzle making.
FAQ
Does IIII mean 4?
Historically it did — Roman abacuses and some inscriptions use IIII often. The standard form is IV, and this tool follows it, so IIII is rejected rather than returned as 4.
Why is 3999 the limit?
It is the conventional boundary of Roman notation; beyond it the Romans used overlines for a factor of a thousand, which is a different system entirely. The tool therefore caps at 1 to 3999 and says so beyond that.
Is the symbol sum the same as the number?
No, and that is the interesting part. MMXXIV adds up to 1000+1000+10+10+1+5 = 2026 while it denotes 2024 — the difference comes from the subtractive IV, which is 5-1=4 rather than 1+5=6. The figure tells you how much subtraction a numeral uses.
What is MMMCMXCIX?
3999, the largest Roman numeral, breaking down as 1000+1000+1000+900+90+9.