How to use the Number System Converter
- 1. Enter a numberType a whole number. Spaces and commas are ignored.
- 2. Pick its baseSay if it is decimal, binary, octal or hex.
- 3. See all fourGet every base, plus how many bits the number needs.
How the four number systems work
Each system uses a different number of digits. Decimal uses ten, binary uses two (0 and 1), octal uses eight (0 to 7) and hexadecimal uses sixteen (0 to 9, then A to F). Each position is worth the base times the position to its right.
Take the decimal number 255 as an example:
- Binary: 1111 1111, which is 128 + 64 + 32 + 16 + 8 + 4 + 2 + 1.
- Octal: 377, which is 3×64 + 7×8 + 7.
- Hex: FF, which is 15×16 + 15.
Hex is popular because one hex digit is exactly 4 binary digits, so long binary values shrink to something readable. You see it in memory addresses and colour codes, which you can explore with the HEX to RGB converter.
Why large numbers stay exact
Normal JavaScript numbers lose accuracy above 9,007,199,254,740,991. That is why many online converters quietly give wrong answers for 64-bit values. This tool uses BigInt, which does exact whole-number maths at any size, up to 5,000 digits here.
The largest unsigned 64-bit number, 18,446,744,073,709,551,615, converts to FFFF FFFF FFFF FFFF in hex with no rounding. Decimal fractions such as 3.14 are not supported.
You can paste values with common prefixes like 0x, 0b and 0o. Negative numbers are shown with a minus sign, not in two's complement form. Grouped digits in the result are only for reading, and Copy gives you the plain digits. Studying encoding too? See how bytes become text in the Base64 encoder.
Frequently asked questions
Can it handle 64-bit numbers?
Yes, and far larger. It uses exact BigInt maths, up to 5,000 digits.
Does it support decimals like 10.5?
No. It converts whole numbers only, which may be negative.
Does case matter for hex?
No. You can type ff or FF. The result uses capital letters.
Is this tool free?
Yes, it is free. We ask for your name and WhatsApp number once when you see your result, and other Uncodemy tools then open without the form.