About the Number Base Converter
Tezmy's Number Base Converter switches numbers between binary (base 2), octal (base 8), decimal (base 10), hexadecimal (base 16) and any other base up to 36. Type a number, tell it which base it's in, and see it in every other base at once, neatly grouped so long binary and hex values are easy to read. It uses exact big-number maths, so even numbers with hundreds of digits convert without rounding.
Updated October 2026
How to use the Number Base Converter
- 1Choose the base your number is in, like Decimal or Binary.
- 2Type the number. Prefixes like 0x and 0b are fine.
- 3Read it in binary, octal, decimal, hex and an extra base.
- 4Copy the result you need.
Number bases in simple words
The base tells you how many digits a system uses. Decimal (base 10) uses 0–9. Binary (base 2) uses only 0 and 1, the language of computers. Octal (base 8) uses 0–7, and hexadecimal (base 16) uses 0–9 and A–F. The same amount can be written in any base: 255 in decimal is 11111111 in binary and FF in hex.
How to convert binary to decimal by hand
Each binary digit is worth double the one to its right: 1, 2, 4, 8, 16 and so on. Add the values where there's a 1. For 1011: 8 + 0 + 2 + 1 = 11. To go the other way, divide by 2 repeatedly and read the remainders from bottom to top.
Where you'll meet these bases
- Hexadecimal: colour codes (#FF0000), memory addresses and data in programming.
- Binary: computer science lessons, networking and bit flags.
- Octal: Unix file permissions like chmod 755.
- Base 36: short IDs and URL codes that use digits and letters.
Big numbers without rounding
Many calculators round very large numbers. This converter uses exact big-number maths, so long values like 64-bit numbers or cryptographic keys convert digit-perfectly. Negative numbers are supported with a minus sign. If you are decoding old text, the Roman Numeral Converter shows the same number in another notation. The Unit Converter handles measurements, and the Color Converter turns hex codes into RGB values, which are base-16 numbers in disguise.
Features
- Binary, octal, decimal and hex
- Any base from 2 to 36
- Exact for very long numbers
- Negative numbers supported
- Readable digit grouping
- Clear errors for invalid digits
Frequently asked questions
How do I convert binary to decimal?
Each binary digit is worth double the one to its right: 1, 2, 4, 8, 16 and so on. Add up the values where there's a 1. For example, 1011 = 8 + 0 + 2 + 1 = 11.
How do I convert decimal to hexadecimal?
Divide by 16 repeatedly and write down the remainders, using A–F for 10–15, then read them from last to first. 255 becomes FF. This tool does it instantly.
Why do programmers use hexadecimal?
One hex digit is exactly 4 binary digits, so hex is a short, readable way to write binary data, memory addresses and colours like #FF8800.
What bases above 16 look like?
They continue the alphabet: base 36 uses 0–9 and A–Z. It's used for short IDs and codes.
Can it handle very large numbers?
Yes. It uses exact integer maths, so there's no rounding, even with hundreds of digits.
What is 10 in binary?
10 in decimal is 1010 in binary: 8 + 2 = 10.
How do I convert hex to binary?
Choose hexadecimal as the input base and type the value. Each hex digit becomes exactly four binary digits, shown grouped for easy reading.
Is it useful for computer science homework?
Yes. Check your answers for binary, octal and hex conversions, and use the hand methods in this guide to show your working.
What is FF in decimal?
FF in hexadecimal is 255 in decimal: F is 15, so 15 × 16 + 15 = 255.
Is it free?
Yes. No sign-up, and it works offline once loaded.