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Number to Roman Numeral Converter

Convert whole numbers to canonical modern Roman numerals and decode only valid canonical forms from I to MMMCMXCIX.

Quick Reference
I
1
V
5
X
10
L
50
C
100
D
500
M
1000
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About This Tool

What it does

Converts whole numbers from 1 to 3,999 to the common modern subtractive form and rejects non-canonical input such as IIII, VX, IIV or MMMM.

Who it's for

Students, editors and designers who need a consistent modern Roman-numeral form. Historical inscriptions may use valid-looking additive variants that this strict converter intentionally rejects.

Your privacy

All validation and conversion happens locally in your browser.

Convention and sources

The supported convention uses I, V, X, L, C, D and M with the subtractive pairs IV, IX, XL, XC, CD and CM, limited to 1–3,999. Historical practice was not fully standardised. Sources reviewed 23 June 2026: UK National Archives; Unicode Standard, numeral characters.

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Frequently Asked Questions

It uses the common modern canonical form with I, V, X, L, C, D and M and the subtractive pairs IV, IX, XL, XC, CD and CM.
Roman-numeral practice varied historically, but this tool deliberately accepts one canonical modern spelling per value. For example, 4 must be IV and 9 must be IX.
Whole numbers from 1 through 3,999 are supported. The canonical range runs from I through MMMCMXCIX. Zero, negatives, fractions and values above 3,999 are outside this tool’s notation.
No. A value such as 14.9 is rejected rather than silently truncated to XIV.
2026 is MMXXVI: MM is 2,000, XX is 20 and VI is 6.
XIV is 14: X is 10 and IV is 4.
Yes. Lowercase input is converted to uppercase before strict validation.
Yes. It runs locally in your browser and does not send the entered number or numeral to ToolBullet.
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