Canonical notation
The converter validates standard subtractive notation such as IV, IX, XL, XC, CD, and CM.
Supported range
Traditional compact Roman notation on this page is limited to whole numbers from 1 through 3999.
Strict validation
Non-canonical strings such as repeated subtractive forms are rejected even if a loose parser could assign them a number.
Frequently asked questions
Does conversion happen in my browser?
Yes. These value conversions run in the browser and do not require an account.
Should I verify a critical conversion?
Yes. For engineering, laboratory, medical, financial, legal, or safety-critical work, verify the unit definition and result against an authoritative standard for your context.