Number Base Converter: Binary, Octal, Decimal, Hex (Base 2–36)
Convert a whole number between number systems and see binary, octal, decimal and hex together, with the working.
- Nothing you type is stored
- Free
- No signup
Result
FF₁₆
- Binary (2)
- 11111111
- Octal (8)
- 377
- Decimal (10)
- 255
- Hex (16)
- FF
Show working
- 255 ÷ 16 = 15 … F
- 15 ÷ 16 = 0 … F
- ↑ FF₁₆
How to use
- Type the number and pick its base.
- Pick the base to convert to (or "Other" for any base 2–36).
- Read the result; open "Show working" for the division steps.
Good to know
In base b, each digit is multiplied by a power of b: 1011₂ = 1×8 + 0×4 + 1×2 + 1×1 = 11. To go from decimal to base b, divide by b repeatedly and read the remainders from bottom to top.
Bases above 10 use letters for digits: A = 10 up to Z = 35. Hex is common in colours (#FF5A1F), memory addresses and error codes; binary and octal appear in computer science exams and file permissions (755).
Calculations use exact big-integer arithmetic, so 64-bit values like FFFFFFFFFFFFFFFF convert without rounding. Fractions are not supported; negative numbers keep a minus sign (not two's complement).
Questions
What is 255 in binary and hex?
11111111 in binary and FF in hex.
How do I convert binary to decimal?
Multiply each digit by its power of 2 and add: 1101 = 8 + 4 + 0 + 1 = 13.
Why does hex use letters?
Base 16 needs 16 digits, so A–F stand for 10–15.
Can it convert fractions?
No, only whole numbers.
Is anything I type sent to a server?
No. The conversion runs on your device and nothing is stored.