Number Format Converters You Might Not Know You Needed: Words, Roman Numerals, and Number Bases

Numbers get represented in more formats than the plain decimal digits we default to, and converting between them by hand is tedious in ways that are easy to underestimate until you actually need to do it.

Numbers as written words

Legal documents, checks, and formal contracts often require an amount to be spelled out in words alongside the numeral, specifically to prevent a numeral from being altered after signing — "One Thousand Two Hundred Only" next to 1,200 makes tampering with the digits alone useless. This gets more complicated with India's numbering system, which groups digits differently than the international system — lakhs and crores instead of millions and billions past a certain point — meaning a number like 1,000,000 is written as "Ten Lakh," not "One Million," under the Indian convention. Manually converting a large number into words correctly, in either system, is easy to get wrong past a few digits. The Number to Words Converter handles both the international and Indian numbering systems automatically.

Roman numerals

Roman numerals still show up in specific, recurring contexts — clock faces, book chapter numbering, movie sequel titles, and the naming of monarchs and Olympic games. The system uses combinations of letters where a smaller value placed before a larger one means subtraction (IV = 4) and placed after means addition (VI = 6) — a rule that's simple in isolation but easy to apply inconsistently by hand once numbers get into the hundreds or thousands. The Roman Numeral Converter converts in both directions on one page, useful for anything from formatting a chapter heading to decoding a copyright year written in Roman numerals on an old film.

Number bases: binary, octal, decimal, hexadecimal

Different number bases represent the same value using a different number of unique digits — decimal (base 10) is what we use daily, binary (base 2) is the foundation of how computers represent all data, hexadecimal (base 16) is commonly used as a compact, human-readable way to represent binary data like color codes or memory addresses, and octal (base 8) shows up less often today but still appears in specific contexts like Unix file permissions. Converting between bases by hand — especially binary to hexadecimal for a long value — is slow and a common source of off-by-one errors when done manually digit by digit.

Where base conversion actually comes up

Reading a hex color code and understanding what it represents in decimal RGB values, interpreting a Unix file permission like 755 (which is octal), debugging a low-level programming issue where a value is displayed in an unfamiliar base, or simply learning how computers represent numbers internally for a computer science course. The Base Number Converter converts between binary, octal, decimal, and hexadecimal instantly, without needing to work through the positional-value math by hand.

Try them

Spell out a number in words with the Number to Words Converter, convert to or from Roman numerals with the Roman Numeral Converter, or convert between number bases with the Base Number Converter.