Roman Numeral: Convert Numbers to Roman Numerals

When you see "MMXXVI" carved into stone, printed on a copyright notice, or tattooed on someone's arm, you're looking at a number system that has survived over 2,500 years. Roman numerals remain everywhere: movie credits, book chapters, clock faces, building cornerstone dates, and even Super Bowl titles. Yet for most people, reading anything beyond "I, II, III" requires mental gymnastics or a quick internet search.

A Roman numeral converter solves this ancient puzzle instantly. It translates between our familiar Arabic numbers (1, 2, 3...) and the Roman system (I, II, III...), making it easy to decode historical dates, create meaningful tattoos, or understand why your birth year might be written as MCMXC instead of 1990.

This comprehensive guide explains exactly how Roman numerals work, why they have strict limits, how conversion works in both directions, and the common mistakes that lead people to write invalid Roman numbers.

What Is a Roman Numeral Converter?

A Roman numeral converter is a tool that translates numbers between two systems:

• Arabic numerals (Hindu-Arabic system): The 0-9 digits we use daily—1, 25, 1984, 2026

• Roman numerals: The letter-based system using I, V, X, L, C, D, M—I, XXV, MCMLXXXIV, MMXXVI

The converter performs bidirectional translation. Input a regular number like 2026, and it outputs MMXXVI. Input XIX, and it outputs 19.​

The Seven Basic Symbols

Roman numerals use seven letters, each representing a fixed value:​

Symbol	Value
I	1
V	5
X	10
L	50
C	100
D	500
M	1,000

Every Roman numeral is built by combining these seven symbols according to specific rules. There is no symbol for zero—the Romans had no concept of zero as a number.​

The Fundamental Rules of Roman Numerals

Understanding Roman numerals requires mastering three core principles.

Rule 1: Addition (Symbols in Descending Order)

When symbols appear in descending order (largest to smallest, left to right), add their values.​

Examples:

• VI = V + I = 5 + 1 = 6

• XII = X + I + I = 10 + 1 + 1 = 12

• LXVII = L + X + V + I + I = 50 + 10 + 5 + 1 + 1 = 67

Rule 2: Subtraction (Smaller Before Larger)

When a smaller symbol appears immediately before a larger symbol, subtract the smaller from the larger.​​

This "subtractive notation" prevents writing four identical symbols in a row.​​

Standard subtractive combinations:​

• IV = 5 - 1 = 4 (instead of IIII)

• IX = 10 - 1 = 9 (instead of VIIII)

• XL = 50 - 10 = 40 (instead of XXXX)

• XC = 100 - 10 = 90 (instead of LXXXX)

• CD = 500 - 100 = 400 (instead of CCCC)

• CM = 1000 - 100 = 900 (instead of DCCCC)

Important: Only these six combinations are valid. You cannot create random subtractive pairs. For example, "IC" for 99 is invalid—the correct form is XCIX (90 + 9).​​

Rule 3: Repetition Limits

Symbols can repeat, but with strict limits:​

Can repeat up to 3 times: I, X, C, M​

• III = 3

• XXX = 30

• CCC = 300

• MMM = 3,000

Cannot repeat: V, L, D​

These symbols represent midpoints (5, 50, 500). Repeating them would be inefficient—VV would just be X.​

How to Convert Numbers to Roman Numerals (Step-by-Step)

Converting Arabic numbers to Roman numerals follows a systematic breakdown process.

The Conversion Method

Step 1: Break the number into place values (thousands, hundreds, tens, ones)

Step 2: Convert each place value separately

Step 3: Combine from left to right (largest to smallest)

Example 1: Converting 2026

Step 1: Break down by place value

• 2026 = 2000 + 0 + 20 + 6

Step 2: Convert each component

• 2000 = MM (M + M)

• 0 = (nothing)

• 20 = XX (X + X)

• 6 = VI (V + I)

Step 3: Combine

• MMXXVI​

Example 2: Converting 1984

Step 1: Break down

• 1984 = 1000 + 900 + 80 + 4

Step 2: Convert each component​

• 1000 = M

• 900 = CM (subtractive: 1000 - 100)

• 80 = LXXX (L + X + X + X)

• 4 = IV (subtractive: 5 - 1)

Step 3: Combine

• MCMLXXXIV​

Example 3: Converting 49

Step 1: Break down

• 49 = 40 + 9

Step 2: Convert

• 40 = XL (subtractive: 50 - 10)

• 9 = IX (subtractive: 10 - 1)

Step 3: Combine

• XLIX​

How to Convert Roman Numerals to Numbers

Converting Roman numerals to Arabic numbers requires reading left to right and applying addition or subtraction rules.

The Algorithm

Step 1: Start from the left

Step 2: Compare each symbol with the symbol to its right

Step 3:

• If current symbol ≥ next symbol → Add current value

• If current symbol < next symbol → Subtract current value

Step 4: Continue until you reach the end

Example 1: Converting XLIV to a Number

XLIV = 44

Reading left to right:

• X (10) < L (50) → Subtract: -10

• L (50) > I (1) → Add: +50

• I (1) < V (5) → Subtract: -1

• V (5) is last → Add: +5

Calculation: -10 + 50 - 1 + 5 = 44​

Example 2: Converting MCMXCIX to a Number

MCMXCIX = 1999

Reading left to right:

• M (1000) > C (100) → Add: +1000

• C (100) < M (1000) → Subtract: -100

• M (1000) > X (10) → Add: +1000

• X (10) < C (100) → Subtract: -10

• C (100) > I (1) → Add: +100

• I (1) < X (10) → Subtract: -1

• X (10) is last → Add: +10

Calculation: 1000 - 100 + 1000 - 10 + 100 - 1 + 10 = 1999​

The 3,999 Limitation

The most important constraint of standard Roman numerals: you cannot write numbers above 3,999 using basic symbols.​

Why 3,999 Is the Maximum

The largest standard Roman numeral is MMMCMXCIX (3,999).​

Breaking it down:

• MMM = 3000

• CM = 900

• XC = 90

• IX = 9

• Total: 3,999

To write 4,000, you would need MMMM (four Ms), but this violates the "no more than three repetitions" rule. The next value symbol (5,000) doesn't exist in the basic system.​

Writing Numbers Beyond 3,999

Ancient Romans developed notation systems for larger numbers:​​

Vinculum (overline): A horizontal line over a numeral multiplies it by 1,000​​

• V̅ = 5,000

• X̅ = 10,000

• L̅ = 50,000

• C̅ = 100,000

• M̅ = 1,000,000

Example: 4,000 = M̅V̅ (instead of illegal MMMM)​

Box notation: Three-sided box multiplies by 100,000​

These extensions allow writing numbers up to hundreds of millions, though they become increasingly impractical and historically inconsistent.​

Converting Dates to Roman Numerals

One of the most popular uses of Roman numeral converters is translating dates—birthdays, anniversaries, historical events.

Birthday Roman Numeral Conversion

To convert a birthday like March 15, 1985:

Option 1: Full date (Month/Day/Year)

• 03/15/1985 → III.XV.MCMLXXXV

Option 2: Year only (most common for tattoos)

• 1985 = 1000 + 900 + 80 + 5

• 1985 = MCMLXXXV​

Current Year: 2026

2026 = MMXXVI

• MM = 2000

• XX = 20

• VI = 6​

Super Bowl LIX (2025)

LIX = 59

• L = 50

• IX = 9

• Total: 59​

Common Mistakes and Invalid Roman Numerals

Even with rules, people make predictable errors when converting.

Mistake 1: Four Repetitions

Wrong: IIII for 4
Correct: IV​​

While some clock faces use IIII for aesthetic symmetry (controversial), it violates standard rules. In most contexts, use IV.​

Mistake 2: Invalid Subtractive Pairs

Wrong: IC for 99 (I cannot subtract from C)
Correct: XCIX (90 + 9)​

Valid subtraction rules:​​

• I can only subtract from V and X

• X can only subtract from L and C

• C can only subtract from D and M

Mistake 3: Repeating V, L, or D

Wrong: VV for 10
Correct: X​

These symbols never repeat. VV would be written as X, LL as C, DD as M.​

Mistake 4: Multiple Subtractions

Wrong: IIX for 8 (attempting to subtract 2)
Correct: VIII​

Only one symbol can be subtracted at a time. You cannot write IIX (10 - 2). The correct form is VIII (5 + 3).​

Mistake 5: Out-of-Order Symbols

Wrong: MMVXX (mixing order)
Correct: MMXXV​

Symbols must always appear in descending value order (with the exception of valid subtractive pairs). Largest values go left, smallest right.​

When to Use Roman Numerals

Roman numerals have specific modern applications where they remain standard.

Copyright notices: © MMXXVI (2026)

Building cornerstones: Established MCMXXX (1930)

Book prefaces: Chapters I-XII (1-12)

Movie sequels: Rocky II, Star Wars Episode IV

Sporting events: Super Bowl LIX (59), Olympics XXXIII (33)

Clock faces: Traditional analog clocks

Outlines: I. Introduction, II. Body, III. Conclusion

Monarchs and popes: Elizabeth II, Pope Francis (formerly Benedict XVI)

Tattoos: Meaningful dates in aesthetic script

When NOT to Use Roman Numerals

Roman numerals are terrible for:

Mathematics: No zero, no place value system, no easy arithmetic​

Large numbers: Numbers above 3,999 become awkward or require special notation​

Fractions: Roman numerals have no decimal point or fraction system​

Accounting: Imagine balancing a checkbook in Roman numerals—impossible

Science: Any calculation requiring precision

Roman numerals are purely symbolic and ceremonial in modern use. They mark tradition, prestige, and permanence—not practical calculation.​

Frequently Asked Questions

What is MMXXV in regular numbers?

MMXXV = 2025. Breaking it down: MM (2000) + XX (20) + V (5) = 2,025.​

How do you write your birthday in Roman numerals?

Convert your birth year to Roman numerals. For example, if born in 1990: 1990 = MCMXC (M=1000, CM=900, XC=90). Some people include the full date: 07.15.1990 = VII.XV.MCMXC.​

Why is 4 written as IV and not IIII?

Standard Roman numeral rules use subtractive notation to avoid writing four identical symbols in a row. IV (5-1) is cleaner than IIII. However, some traditional clock faces use IIII for visual balance with VIII on the opposite side.​​

What is the Roman numeral for 3,999?

3,999 = MMMCMXCIX. This is the largest number expressible using standard Roman numeral symbols without special notation.​

Can you write 1 million in Roman numerals?

Using basic symbols, no. With vinculum notation (overline multiplying by 1,000), 1 million = M̅ (M with a line over it). However, this extended notation is not universally recognized.​​

How do you convert MCMXCIX to a number?

MCMXCIX = 1999. Reading left to right with subtraction rules: M (1000) + CM (900) + XC (90) + IX (9) = 1,999.​

What does XIII mean?

XIII = 13. X (10) + III (3) = 13.​

Why don't Roman numerals have a zero?

Ancient Romans had no concept of zero as a number. Their numeral system developed from tally marks and counting systems that started at 1. Zero as a mathematical concept came from India centuries later.​

What is 49 in Roman numerals?

49 = XLIX. Breaking it down: XL (40, from 50-10) + IX (9, from 10-1) = 49.​​

Are there Greek numerals like Roman numerals?

Yes, ancient Greeks used two systems: the earlier Attic numerals (similar to Roman) and the later alphabetic numerals using Greek letters. However, Greek numerals are rarely used today, while Roman numerals remain common.​