Decimal to Binary

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Quick answer

To convert decimal to binary, divide by 2 repeatedly and read the remainders from last to first — for example 10 → 1010. TryDevSnip's converter does it instantly and exactly, even for large numbers, all in your browser.

Open decimal → binary converter

Decimal to binary chart

Decimal	Binary
2	10
4	100
8	1000
10	1010
16	10000
32	100000
64	1000000
100	1100100
128	10000000
255	11111111

Reverse or related: binary to decimal · decimal to hex · hex to decimal · all bases

Worked example: 42

Every positional number system works the same way — each digit is multiplied by the base raised to its position, counting from zero on the right. For 42 in decimal:

Digit	Place	Weight	Contribution
4	10¹	10	40
2	10⁰	1	2
Total (decimal)			42

Written in binary that is 0b101010.

Quick reference

Decimal	decimal	binary
1	1	1
2	2	10
4	4	100
8	8	1000
10	10	1010
16	16	10000
32	32	100000
64	64	1000000
100	100	1100100
128	128	10000000
255	255	11111111
256	256	100000000

Things that trip people up

Prefixes are notation, not value. 0b1010,0o12, 0xA and 10 can all denote the same quantity. Strip the prefix before parsing, or tell the parser which base you meant.
Leading zeros can change the base. In several languages a leading0 historically meant octal, so 010 parsed as 8 rather than 10. Passing an explicit radix avoids the whole class of bug.
Hex letters are case-insensitive. 0xff and0xFF are the same number; only presentation differs.
Grouping is for humans. Binary is usually read in nibbles of four (1111 1111) because each nibble maps to exactly one hex digit — which is why hex is the usual shorthand for binary data.

Frequently asked questions

How do I convert decimal to binary?

Divide the number by 2 repeatedly, writing down the remainders (0 or 1) from last to first. For example 10 → 1010. Or paste it into the converter and read the binary instantly.

What is 255 in binary?

255 (decimal) is 11111111 in binary — eight 1-bits, exactly one full byte.

Does it work for large numbers?

Yes. The converter uses BigInt, so large decimals convert to exact binary strings without losing bits.

Is my input uploaded?

No. TryDevSnip converts locally in your browser. Nothing you type is uploaded to our servers for processing.