Roman Numeral Converter: Numbers to Roman and Back

Type a number to write it in Roman numerals, or a Roman numeral such as MCMXCIV to read it as a number.

Converting numbers to Roman numerals: rules and a worked example

Roman numerals combine seven symbols (I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1,000) that are added up, except when a smaller symbol stands before a larger one: it is then subtracted (IV = 4, CM = 900). The converter works both ways for numbers from 1 to 3,999, the ceiling of the notation without an overline.

How the tool converts

From number to Roman, the tool walks through a table of 13 values from largest to smallest: M (1,000), CM (900), D (500), CD (400), C (100), XC (90), L (50), XL (40), X (10), IX (9), V (5), IV (4), I (1). As long as the remainder is greater than or equal to a value, it writes the symbol and subtracts the value. The six subtractive pairs (CM, CD, XC, XL, IX, IV) give the standard form: 4 is written IV, never IIII.

Example: 1994 = 1,000 + 900 + 90 + 4, i.e. M + CM + XC + IV = MCMXCIV. Likewise 2026 gives MMXXVI and 3,999 gives MMMCMXCIX.

From Roman to number, the tool reads left to right: if the next letter is worth more than the current one, it adds the difference (C then M = 900); otherwise it adds the letter's value. MCMXCIV turns back into 1994.

Limits

  • The Number field only accepts whole numbers from 1 to 3,999. For 0, a negative number or 4,000 and above, the Roman field stays empty; the overline (vinculum) used for thousands is not supported.
  • The Roman field keeps only I, V, X, L, C, D and M and accepts only the standard form: IIII, IM, VX or MMMM show “Invalid input” and leave the Number field empty, since 4 is written IV, 999 CMXCIX, 5 V, and 4,000 has no form without an overline. An entry is accepted when converting it back gives the same string.
  • There is no zero, no fraction and no negative number in Roman notation.

Frequently Asked Questions

How do you write 2026 in Roman numerals?

2026 is MMXXVI: MM for 2,000, XX for 20 and VI for 6. Type 2026 into the Number field to get it straight away.

What is the largest number you can write in Roman numerals?

With the seven standard letters and no symbol repeated more than three times, the maximum is 3,999, written MMMCMXCIX. Larger numbers used an overline that multiplies by 1,000; the tool stops at 3,999.

Why is 4 written IV and not IIII?

Standard notation uses subtraction: an I placed before V takes away 1, so IV = 4 and IX = 9. Only I, X and C are used this way, before the next two higher symbols (I before V and X, X before L and C, C before D and M). IIII still appears on some clock faces.

How do you read a Roman numeral like MCMXLVIII?

Split it into groups: M (1,000) + CM (900) + XL (40) + VIII (8) = 1,948. A smaller letter placed before a larger one is subtracted; otherwise it is added.

Is this tool really free?

Yes, all tools on Kristools are 100% free and accessible without registration.

Is my data protected?

Yes. All processing is performed directly and securely inside your browser. No personal data is sent to our servers.