Binary to Decimal Converter
Convert binary ↔ decimal with the powers of 2 method. Example: 11111111 → 255. Free and private in your browser.
BinaryDecimal
255
How to convert binary to decimal by hand
- Write the binary digits. The rightmost bit is 2⁰ (value 1).
- Under each bit, write its place value: … 128, 64, 32, 16, 8, 4, 2, 1.
- Add every place value where the bit is 1. Ignore zeros.
- The sum is the decimal number.
1 0 1 0
8 4 2 1
8 + 0 + 2 + 0 = 10
For decimal to binary, divide by 2 and read remainders bottom-up — or swap the converter. Guides: powers of 2 · division method.
Binary to decimal examples
| Binary | Decimal |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 10 | 2 |
| 1010 | 10 |
| 1111 | 15 |
| 10000000 | 128 |
| 11111111 | 255 |
| 100110011 | 307 |
Also see binary to hex and the full base converter.
Frequently Asked Questions
How do I convert binary to decimal?
Write place values under each bit (… 128 64 32 16 8 4 2 1 for 8 bits). Add the values where the bit is 1. Example: 11111111 → 128+64+32+16+8+4+2+1 = 255.
How do I convert decimal to binary?
Divide by 2 repeatedly and collect remainders, or subtract the largest power of 2 that fits. Swap the converter to enter a decimal and read binary.
What is 1010 in decimal?
8+2 = 10. Bits from the right: 0×1 + 1×2 + 0×4 + 1×8.
Is this binary to decimal converter free?
Yes — free, no signup, and all math stays in your browser.