Converters · Number tools
Roman to Integer Converter
Decode any Roman numeral to an integer instantly with this free roman numeral to number converter — a strict roman numeral decoder for the standard 1–3,999 range plus extended overline (vinculum) notation to 3,999,999. See every conversion step, validate tricky inputs like IIII, and batch-convert whole lists of roman numerals to numbers. 100% client-side, nothing leaves your browser.
✓ Private by design — decoding runs locally in JavaScript
Enter a Roman numeral to convert roman numerals to numbers — the “Show your work” table breaks every decode into its addition and subtraction steps. Lowercase is accepted.
Paste one Roman numeral per line (commas work too) to run this roman to number converter in bulk.
How to convert Roman numerals to numbers
Learning how to read Roman numerals comes down to five habits — the decoder above automates all of them, but knowing the rules helps you trust its verdicts.
- Normalize the input. Uppercase everything and strip spaces — this roman numeral decoder also accepts lowercase, so mdclxvi decodes the same as MDCLXVI.
- Scan left to right. Add each symbol’s value; when a smaller symbol stands before a larger one, subtract it instead. That single rule turns MMXXVI into 1000+1000+10+10+5+1 = 2026.
- Validate strictly. Only the six subtractive pairs — IV, IX, XL, XC, CD, CM — are legal. IIII, VV, and IC are rejected with the correct spelling suggested.
- Read the overline for thousands. In extended vinculum roman numerals a line over a symbol multiplies it by 1,000: V̅ is 5,000, I̅V̅ is 4,000. Type an underscore prefix (_V) if you cannot type the overline character.
- Batch-convert lists. The “Batch convert” tab decodes a whole column at once when you need to translate Roman numerals to numbers in bulk, with CSV export for spreadsheets.
Roman numeral reference
The seven symbols
| Symbol | Value |
|---|---|
| I | 1 |
| V | 5 |
| X | 10 |
| L | 50 |
| C | 100 |
| D | 500 |
| M | 1,000 |
Subtractive pairs
| Pair | Value | Means |
|---|---|---|
| IV | 4 | 5 − 1 |
| IX | 9 | 10 − 1 |
| XL | 40 | 50 − 10 |
| XC | 90 | 100 − 10 |
| CD | 400 | 500 − 100 |
| CM | 900 | 1000 − 100 |
Common invalid forms (and what to write instead)
| Invalid input | Why it is rejected | Write instead |
|---|---|---|
| IIII | No symbol repeats more than 3 times | IV = 4 |
| VV | V, L, and D never repeat | X = 10 |
| LL | V, L, and D never repeat | C = 100 |
| DD | V, L, and D never repeat | M = 1,000 |
| IC | I only subtracts from V and X | XCIX = 99 |
| IM | I only subtracts from V and X | CMXCIX = 999 |
| IL | I only subtracts from V and X | XLIX = 49 |
| XM | X only subtracts from L and C | CMXC = 990 |
| VX | V never subtracts | V = 5 |
| IXI | Only one subtraction per place value | X = 10 |
Roman numerals 1–100
| Number | Roman | Number | Roman | Number | Roman | Number | Roman |
|---|
Tip: 4 is written IV, not IIII — the one place you will see IIII is on traditional clock faces.
Which tool do you need?
This tool: reading numerals
Decode one Roman numeral — or a whole list — into integers, with strict validation, step-by-step breakdowns, and overline notation to 3,999,999.
Writing numerals
Need the reverse direction? Our integer to Roman numerals converter turns 2026 into MMXXVI, with the same extended notation.
Calendar dates
Decoding a date like VII.X.MMXXVI? Day, month, and year must be decoded separately — use our date to Roman numerals converter.
Frequently asked questions
How do I convert Roman numerals to integers?
Read the numeral left to right and add each symbol’s value — unless a smaller symbol comes before a larger one, in which case subtract it. That is the whole roman-to-integer algorithm: in MMXXVI, M+M+X+X+V+I = 1000+1000+10+10+5+1 = 2026. Only six subtractive pairs are legal — IV, IX, XL, XC, CD, CM — and the decoder above rejects anything else, like IC or IIII, instead of guessing.
What is MMXXVI in numbers?
MMXXVI is 2026. Break it into tokens: M (1000) + M (1000) + X (10) + X (10) + V (5) + I (1) = 2026. Paste it into the roman numeral decoder above to see the full step-by-step table.
What is MCMXCIV in numbers?
MCMXCIV is 1994: M (1000) + CM (900) + XC (90) + IV (4) — the classic mcmxciv to number example, because it packs three different subtractive pairs — CM, XC, and IV — into a single numeral.
Is IIII a valid Roman numeral?
No — strict Roman form never repeats a symbol more than three times in a row, so 4 must be written IV. This roman numeral validator rejects IIII and suggests IV instead. One real-world exception: many clock faces traditionally use IIII for 4, a stylistic choice clockmakers kept for visual symmetry, not a rule of the numeral system.
Why is IC not valid for 99?
Only I, X, and C may be used subtractively, and each only before the next two higher symbols: I before V or X, X before L or C, C before D or M. IC breaks the rule because I cannot subtract from C — 99 is written XCIX (90 + 9). Type IC into the decoder and it will reject it while suggesting XCIX as the strict spelling.
How do you read Roman numerals with a line over them?
That is vinculum (overline) notation: a line over a symbol multiplies its value by 1,000. So V̅ is 5,000 and I̅V̅ is 4,000. This decoder reads overlined input two ways: paste characters carrying a combining overline, or type an underscore before the symbol, like _V for 5,000. Extended decoding works up to 3,999,999.
How do Roman numerals convert to decimal step by step?
Take MMXXVI: read left to right, and add a symbol’s value unless the next symbol is larger, then subtract. M (next M, equal) → +1000 = 1000; M → +1000 = 2000; X (next X) → +10 = 2010; X → +10 = 2020; V (next I, smaller) → +5 = 2025; I → +1 = 2026. The “Show your work” table above performs exactly these roman numerals to decimal — that is, roman numerals to arabic numerals — steps for any numeral you enter.
How do I read Roman numerals on a clock?
Clock faces put XII at the top and run clockwise down to XI. For 4, most clocks show IIII rather than IV — pure tradition: clockmakers liked the visual balance of IIII opposite VIII. For 8, clocks always show VIII, never IIX. When you decode roman numerals on clocks, remember that IIII means 4 there even though a strict validator flags it everywhere else.
What number is XL in Roman numerals?
XL is 40 — X (10) placed before L (50) means 50 − 10. Its common neighbors: XXXIX is 39, XLI is 41, and XLIV is 44 (40 + 4).
Is there a Roman numeral for zero?
No. The Romans had no zero and no negative numbers — the smallest Roman numeral is I (1). This decoder rejects 0, negatives, and decimals with an honest error instead of inventing an answer.
How do I decode a Roman numeral date like VII.X.MMXXVI?
A calendar date has three parts — day, month, year — so decode each part separately: VII is 7, X is 10, and MMXXVI is 2026, giving 7 October 2026. For birthdays, anniversaries, and tattoos, use our dedicated date to Roman numerals converter, which validates real calendar dates including leap years.
What is the difference between a Roman-to-integer decoder and an integer-to-Roman converter?
Direction. This page is a roman numeral decoder: it reads numerals and returns numbers, so MMXXVI becomes 2026. An integer-to-Roman converter does the reverse: it writes numerals from numbers, so 2026 becomes MMXXVI. Use our integer to Roman numerals converter when you need to write a numeral; stay here when you need to read one.
Can I decode a list of Roman numerals at once?
Yes — open the “Batch convert” tab, paste one numeral per line (commas work too), and get a results table with every integer. You can copy all results or download them as CSV or TXT for spreadsheets.
What is the largest Roman numeral?
With the standard seven symbols, the largest Roman numeral is MMMCMXCIX, which is 3,999: MMM (3,000) + CM (900) + XC (90) + IX (9). Anything bigger needs vinculum overline notation — 4,000 is written I̅V̅, and this decoder reads overlined numerals up to 3,999,999.
Which subtractive pairs are valid in Roman numerals?
Exactly six: IV (4), IX (9), XL (40), XC (90), CD (400), CM (900). The full rules: only I, X, and C can subtract; V, L, and D never subtract and never repeat; I, X, C, and M repeat at most three times. Anything else — IL, IC, XM, VV, IIII — is rejected by the strict validator, which suggests the correct spelling.
Free tool by NRTechStudio