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Roman Numeral to Number

Type a Roman numeral below. We'll convert it instantly — and if something's wrong, we'll explain exactly why with a helpful hint.

Got a number to convert? Try Number to Roman →

How to Read a Roman Numeral

Every Roman numeral is constructed from just seven core symbols. To decode any Roman numeral into a modern number, start with their base values:

I 1
V 5
X 10
L 50
C 100
D 500
M 1000

Additive vs Subtractive Reading

Reading Roman numerals is all about direction. When numerals appear in descending order of size (or equal values), you simply add them from left to right:

  • XVI = 10 + 5 + 1 = 16
  • CLXVI = 100 + 50 + 10 + 5 + 1 = 166
  • MMXXVI = 1,000 + 1,000 + 10 + 10 + 5 + 1 = 2,026

However, when a smaller symbol appears immediately before a larger one, it forms a subtractive pair. Subtract the smaller value from the larger one:

  • IV = 5 − 1 = 4 (not IIII)
  • IX = 10 − 1 = 9 (not VIIII)
  • XL = 50 − 10 = 40 (not XXXX)
  • XC = 100 − 10 = 90 (not LXXXX)
  • CD = 500 − 100 = 400 (not CCCC)
  • CM = 1,000 − 100 = 900 (not DCCCC)

Step-by-step example: Decoding MCMXCIX

To decode a complex multi-digit numeral like MCMXCIX, break it down from left to right into individual symbols and subtractive pairs:

  1. M = 1,000
  2. CM = 1,000 − 100 = 900
  3. XC = 100 − 10 = 90
  4. IX = 10 − 1 = 9

Adding the groups together: 1,000 + 900 + 90 + 9 = 1,999.

How to Convert a Roman Numeral to a Number

Follow this straightforward 3-step method to read and translate any Roman numeral.

1

Scan symbols from left to right

Roman numerals are arranged from highest value to lowest value: thousands (M), hundreds (C, D), tens (X, L), and units (I, V). Look at each character in sequence to identify its base value.

2

Identify the 6 subtractive pairs

Whenever a smaller numeral appears immediately before a larger one, group them together as a subtractive pair: IV=4, IX=9, XL=40, XC=90, CD=400, CM=900. Calculate their value by subtracting the smaller from the larger.

3

Sum all values to find the total

Add together all the individual symbol values and subtractive pair totals. For example, in MCMLXXXIV: M (1,000) + CM (900) + L (50) + XXX (30) + IV (4) = 1,984. The converter above displays this exact addition equation for any valid input.

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Common Mistakes to Avoid

Invalid combinations that frequently catch people out

IL → XLIX (49)

I can only go before V or X

IC → XCIX (99)

I can only go before V or X

VV → X (10)

V can never be repeated

IIII → IV (4)

Max 3 identical symbols in a row

LC → L (50)

L is never used subtractively

VX → V (5)

V, L, and D are never used subtractively

Common Roman Numeral to Number Conversions

Quick reference table for the most commonly searched Roman numeral translations.

I – XX (1 – 20)

I 1
II 2
III 3
IV 4
V 5
VI 6
VII 7
VIII 8
IX 9
X 10
XI 11
XII 12
XIII 13
XIV 14
XV 15
XVI 16
XVII 17
XVIII 18
XIX 19
XX 20

Round Numerals

V 5
X 10
L 50
C 100
CC 200
CD 400
D 500
CM 900
M 1000
MD 1500
MM 2000
MMD 2500
MMM 3000
MMMD 3500
MMMCMXCIX 3999

Notable Numerals

MLXVI 1066
MDCCLXXVI 1776
MCM 1900
MCMLXIX 1969
MCMLXXXIV 1984
MCMXCIX 1999
MM 2000
MMI 2001
MMX 2010
MMXX 2020
MMXXIV 2024
MMXXV 2025
MMXXVI 2026

Frequently Asked Questions

How do you convert a Roman numeral to a regular number?

Read the symbols from left to right. When symbols appear in descending order or are identical, add their values. When a smaller symbol precedes a larger one (like IV, IX, XL, XC, CD, or CM), it represents a subtractive pair—subtract the smaller value from the larger value. Sum all individual values and pairs to get your final number.

What are the 6 subtractive pairs in Roman numerals?

Standard Roman numerals allow only six subtractive pairs: IV=4, IX=9, XL=40, XC=90, CD=400, and CM=900. Only powers of ten (I, X, C) may be placed before the next two higher symbols. Letters like V, L, and D are never used subtractively.

Why are combinations like "IL" or "IC" invalid?

In standard Roman numeral rules, a symbol can only subtract from the next two larger denominations. "I" (1) can only precede "V" (5) or "X" (10). It cannot skip ahead to subtract from "L" (50) or "C" (100). Therefore, 49 must be written as XLIX (40 + 9), and 99 must be written as XCIX (90 + 9).

Why can't Roman numerals repeat more than three times?

Standard notation limits repeating symbols (I, X, C, M) to three in a row to keep numbers concise and easy to read. A fourth repetition is replaced by a subtractive pair (e.g. IIII becomes IV, and XXXX becomes XL). The numerals V, L, and D can never repeat because two of them equal a larger single symbol (VV=X, LL=C, DD=M). Explore all rules on our Roman Numeral Rules page →

What is the highest Roman numeral that can be decoded?

Without special extensions, standard Roman numerals stop at MMMCMXCIX (3,999). For numbers 4,000 and higher, ancient Romans used an overline called a vinculum, where a bar placed over a numeral multiplies its value by 1,000 (such as IV̅ for 4,000 or V̅ for 5,000). Try our Large Number converter →

Why do clock dials use IIII instead of IV for 4?

Clockmakers historically chose IIII over IV for visual symmetry with VIII on the opposite side of the dial, traditional manufacturing customs, and royal preference (King Louis XIV). In modern mathematics and everywhere else, 4 is always written as IV. Learn more on our Clock Numerals page →