Roman Numerals Converter
Convert numbers to Roman numerals and Roman numerals back, 1 to 3999.
What it does
Roman numerals add and subtract letter values instead of positioning digits. Symbols stack downward normally, and a smaller value before a larger one subtracts: IV for four, IX for nine, XL for forty.
The tool above converts both directions between 1 and 3999. It returns the answer with a place by place breakdown so each part stays visible.
Subtractive pairs follow strict rules. Only I, X, and C subtract, and only from the next two higher values: IV and IX, XL and XC, CD and CM. Forms like IL for 49 or XM for 990 break the rules and fail validation here.
Romans had no zero and no fractions in this system, which is why arithmetic stayed on counting boards while numerals labeled chapters, clocks, and cornerstones.
How to use
- Pick the direction first.
- For numbers, enter 1 to 3999.
- For numerals, use letters I V X L C D M in standard order.
- Read the breakdown to check each place value.
Formula
- greedy take
- Largest fitting symbol first guarantees standard form.
- subtractive pairs
- CM, CD, XC, XL, IX, IV prevent four repeats.
- place split
- Thousands, hundreds, tens, ones convert separately then join.
Reading right to left with a running maximum decodes: values below the max so far subtract, the rest add. Validation rejects nonstandard strings like IIII or VV.
Worked example
Example: 2026 to Roman
Number 2026, direction to Roman.
- Thousands: 2000 takes MM.
- Hundreds: 0 takes nothing.
- Tens: 20 takes XX.
- Ones: 6 takes VI.
- Join: MMXXVI.
- Breakdown: MM (2000) + XX (20) + VI (6).
Reference table
| Number | Roman | Number | Roman |
|---|---|---|---|
| 1 | I | 40 | XL |
| 4 | IV | 50 | L |
| 9 | IX | 90 | XC |
| 14 | XIV | 400 | CD |
| 44 | XLIV | 900 | CM |
| 99 | XCIX | 2026 | MMXXVI |
Limits
- Standard range 1 to 3999. Larger needs overlines.
- No zero, negatives, or fractions in the system.
- Nonstandard historic spellings are rejected.
- Clock faces sometimes print IIII for 4 by tradition.
Common mistakes
- Writing IIII or VIIII instead of IV and IX.
- Subtracting across places, like IL for 49. Use XLIX.
- Repeating V, L, or D, which never double.
- Reading CM as 1100 instead of 900.
- Expecting zero. Romans left it blank.
Try it yourself
Quick checks. Answers sit tucked under each question.
58 in Roman?
50 + 8: L + VIII = LVIII.
XCIV as a number?
XC is 90, IV is 4: 94.
Questions
What is 2026 in Roman numerals?
MMXXVI: 2000 plus 20 plus 6.
Why is 4 written IV?
Subtractive rule: smaller before larger subtracts, so IV is 5 minus 1.
How do you write 49?
XLIX: 40 plus 9, never IL.
What is the largest standard numeral?
MMMCMXCIX, which is 3999. Larger values need bar notation.
Did Romans have zero?
No symbol for it. Their system counts without place value.
Why do clocks show IIII?
Tradition and symmetry against VIII. Standard math still writes IV.