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How to Convert Numbers and Roman Numerals

By Tools Star Hub Editorial Team · Published

Standard Roman numerals use I, V, X, L, C, D, and M, with subtractive pairs for 4, 9, 40, 90, 400, and 900. This page converts a whole number from 1 to 3999 into that form, and a valid numeral back into a number.

Repeated letters such as IIII, and pairs such as IC or IL, are not the standard form, so they are rejected. Zero and negative numbers are rejected. 4000 is outside the range.

How to convert numbers and Roman numerals

  1. Enter a whole number from 1 to 3999, or enter a numeral. An empty box is rejected.
  2. Read the other form. 1 is I. 4 is IV. 9 is IX. 40 is XL. 90 is XC. 400 is CD. 900 is CM. 3999 is MMMCMXCIX.
  3. Reject a nonstandard numeral. IIII, IC, and IL are rejected. So are 0, a negative number, and 4000.
How to Convert Numbers and Roman Numerals — Tools Star Hub

Example

Standard values

XIV is 14. MMMCMXCIX is 3999. IIII, IC, IL, an empty box, 0, a negative number, and 4000 are rejected.

FAQ

Why is 4 written IV?
The standard form subtracts I from V. IIII is rejected.
What is the highest number?
3999, written MMMCMXCIX.
Does XIV equal 14?
Yes.
Can I write amounts in English words here?
No. Number to Words does that.

To convert a number from 1 to 3999, or a standard numeral, use the Roman Numeral Converter.

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