Convert numbers to Roman numerals and back. Supports 1 to 3,999 with step-by-step breakdown.
Roman numerals are a numeral system originating in ancient Rome that remained the dominant notation in Europe throughout the Middle Ages and into the Renaissance. They use a combination of seven Latin letters, each representing a fixed value, to express any integer from 1 to 3,999. While largely replaced by Hindu-Arabic numerals (the 0-9 system) for everyday arithmetic, Roman numerals remain in widespread use for clock faces, book chapters, film sequels, sporting events (Super Bowl LVIII), monarchs and popes (King Charles III), copyright years in film credits, and formal documents.
Roman numerals use exactly seven symbols, each with a fixed value. I equals 1. V equals 5. X equals 10. L equals 50. C equals 100 (from Latin "centum"). D equals 500. M equals 1000 (from Latin "mille"). All other numbers are formed by combining these seven symbols according to additive and subtractive rules. The system is base-10 in structure but not positional — the value of a symbol does not depend on its position the way it does in Hindu-Arabic notation. This is why Roman numeral arithmetic is cumbersome: XLII + XXIII requires converting to 42 + 23, computing 65, then converting back to LXV. Use our percentage calculator for quick percentage maths and our fraction calculator for fractional calculations the Romans never had an easy notation for.
| Symbol | Value | Origin | Examples with this symbol |
|---|---|---|---|
| I | 1 | Tally mark (one finger) | I, II, III, IV, VI, IX, XI |
| V | 5 | Hand with fingers (V shape) | V, IV, VI, VII, VIII, XIV |
| X | 10 | Two crossed V marks | X, IX, XI, XL, XC, XIV |
| L | 50 | Unknown origin | L, XL, LI, LX, XC |
| C | 100 | Latin "centum" (hundred) | C, XC, CD, CM, CX |
| D | 500 | Half of CIO (1000 symbol) | D, CD, DC, DCC |
| M | 1000 | Latin "mille" (thousand) | M, CM, MM, MMM, MCM |
The most distinctive and confusing aspect of Roman numerals is subtractive notation. When a symbol of smaller value appears immediately before a symbol of larger value, the smaller is subtracted from the larger. Exactly six subtractive combinations are valid in standard Roman numerals: IV = 4 (5 minus 1), IX = 9 (10 minus 1), XL = 40 (50 minus 10), XC = 90 (100 minus 10), CD = 400 (500 minus 100), CM = 900 (1000 minus 100). These are the only permitted subtractive combinations. You cannot write IC for 99 (must be XCIX), LC for 450 (must be CDL) or VX for 5 (invalid). The rules: only I, X and C can be used subtractively. I can only precede V and X. X can only precede L and C. C can only precede D and M. V, L and D are never subtracted. A symbol can repeat at most three times consecutively — so 4 must be IV (not IIII), and 40 must be XL (not XXXX). Use our square root calculator and our scientific calculator for calculations that Roman numerals make impractical.
Certain Roman numeral values appear frequently in everyday contexts — on clock faces, in film titles, for year numbers and in formal lists. Knowing these by heart eliminates the need for conversion in most real-world situations. The numbers 1-10 are I, II, III, IV, V, VI, VII, VIII, IX, X. Decades: XX=20, XXX=30, XL=40, L=50, LX=60, LXX=70, LXXX=80, XC=90. Hundreds: C=100, CC=200, CCC=300, CD=400, D=500, DC=600, DCC=700, DCCC=800, CM=900. Thousands: M=1000, MM=2000, MMM=3000. Common years: MCMXCIX=1999, MM=2000, MMXX=2020, MMXXIV=2024, MMXXV=2025, MMXXVI=2026. Super Bowl numbers: the game uses Roman numerals exclusively, so knowing that L=50 and C=100 lets you decode any Super Bowl number instantly.
| Roman | Number | Roman | Number | Common Context |
|---|---|---|---|---|
| IV | 4 | XL | 40 | Clock face, chapters |
| IX | 9 | XC | 90 | Clock face, chapters |
| XIV | 14 | CD | 400 | Lists, outlines |
| XIX | 19 | CM | 900 | Centuries |
| XXIX | 29 | MCMXCIX | 1999 | Years in film credits |
| LVIII | 58 | MMXXIV | 2024 | Super Bowl LVIII, year |
Roman numerals developed from Etruscan tally systems and were formalised during the Roman Republic (509-27 BC). They served as the primary numeral system across the Roman Empire and remained dominant in Western Europe well into the 14th century, long after the fall of Rome. Their gradual replacement by Hindu-Arabic numerals (introduced to Europe via Arabic mathematicians) accelerated after Leonardo Fibonacci published "Liber Abaci" in 1202, which demonstrated the superior convenience of positional notation for arithmetic. Today Roman numerals survive in specific cultural domains where their formality and visual distinctiveness are valued. Clock and watch faces use them to suggest tradition and elegance. Film sequels and series use them to sound authoritative (Rocky IV, Star Wars Episode IV). Legal and formal documents number sections in Roman numerals to distinguish them from Arabic-numbered subsections. Olympic Games use them for edition numbers. The Super Bowl uses them to avoid confusion with calendar years — Super Bowl 50 was designated "50" rather than "L" because NFL considered the numeral visually insufficient as a standalone logo, but then reverted to Roman numerals from Super Bowl LI onward.
Traditional clock faces with Roman numerals present a fascinating quirk: most use IIII for 4 rather than the standard IV. This practice dates to at least the 14th century and continues to the present day on traditional clock designs including the famous Big Ben clock tower (officially known as the Elizabeth Tower). Several theories attempt to explain IIII's persistence on clocks: visual symmetry, since IIII on the left of the dial balances the VIII on the right; manufacturing simplicity, since IIII only requires the symbol I repeated, making font sets simpler; historical convention, since King Louis XIV of France reportedly preferred IIII and ordered clock makers to use it; and a theory that IV was considered disrespectful because IV begins the name of the Roman god Jupiter (IVPITER). Whatever the origin, IIII on clock faces is now considered a deliberate stylistic choice rather than an error. Modern numerals on digital devices and formal documents always use IV for 4.
Learning to read and write Roman numerals fluently is a useful cultural literacy skill that comes up more often than expected in daily life. Movie and TV production dates, Super Bowl editions, Olympic year numbers, clock faces, book section numbering, legal document clauses and formal outlines all use Roman numerals. The fastest way to become fluent is to memorise the 13 key values used in our converter reference chart above and practise the subtractive combinations (IV, IX, XL, XC, CD, CM) until they are automatic. Larger numbers are then assembled by combining these building blocks from largest to smallest. MMXXVI (2026): MM (2000) + XX (20) + VI (6). MCMXCIX (1999): M (1000) + CM (900) + XC (90) + IX (9). The pattern for any year: identify the thousands (M repeated), then the hundreds block (C, CD, D, DC, DCC, DCCC, or CM), then the tens block (X, XL, L, LX, LXX, LXXX, or XC), then the ones block (I through IX). Our binary converter covers another ancient-feeling but important number representation system used in computing. Roman numerals continue to hold cultural significance in contexts where tradition, formality and longevity matter. Copyright dates in film and television credits are expressed in Roman numerals partly because they are harder to read quickly, discouraging people from immediately calculating how old the content is. Building cornerstones, legal documents and academic diplomas use Roman numerals for the year because the format suggests permanence and classical authority. Olympic Games editions are numbered in Roman numerals: the XXXIII Summer Olympics were held in Paris in 2024. The World Series, Stanley Cup finals and other major sporting championships use Roman numerals in some contexts. European monarchs and popes are numbered in Roman numerals: Pope Francis is Francis I, King Charles III of the UK is numbered III. Musical theory uses Roman numerals to represent chord functions: I chord (tonic), IV chord (subdominant), V chord (dominant) in any key. This Roman numeral notation is universal across music education regardless of the actual key. Volumes, chapters and sections in formal academic publishing traditionally use Roman numerals for major divisions: Volume XII, Chapter IX, Section III. In legal contracts, Roman numeral sections (Section IV, Paragraph ix) distinguish the structural hierarchy from the numbered subpoints that use Arabic numerals. Our scientific calculator handles complex mathematical operations and our percentage calculator covers everyday number calculations that Roman numerals were never designed to simplify.