Convert one canonical Roman numeral
Convert integers from 1 to 3,999 into Roman numerals, or reverse a numeral into an integer. The symbols are I, V, X, L, C, D and M, with subtractive forms such as IV, IX, XL, XC, CD and CM.
Verify XIV in both directions
Enter 14 in the numeric direction and expect XIV. Choose the reverse direction and XIV becomes 14. Another useful example is 1994, which produces MCMXCIV. Lowercase input is normalized to uppercase when checking a Roman numeral.
Understand why IIII is rejected
Reverse conversion calculates a candidate integer, converts it back into canonical notation and requires that spelling to match. IIII therefore fails, although historical additive conventions sometimes use it. Rejection means the input is outside this converter’s convention, not that every historical use is invalid.
Respect the range and notation
Zero, negative numbers, fractional values, overbars and extended numerals above 3,999 are not supported. Do not remove a sign or an overbar just to obtain a result: that changes the value being represented. Keep the original while checking the visible error.
Choose words when symbols are not the goal
The calculation runs in the browser tab without sending the input to NexaCurrent. Run a known value first, inspect the result and copy it deliberately. Reset clears the work. Use Number to English Words for spelling ordinary numbers, or English Words to Number to read conventional integer phrases.