Binary ⇆ Decimal Converter
Convert a decimal number, an IP address, or binary — in either direction, instantly. Paste 192.168.1.1 and get the binary; paste binary and get it back. Everything runs in your browser.
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Why network engineers need binary
You can pass a networking course by memorising that a /26 is 255.255.255.192. You cannot understand subnetting that way — and it will fail you the moment a question is phrased unusually.
Everything in IP addressing is a binary operation wearing a decimal disguise:
- A subnet mask is just a run of 1s followed by a run of 0s. A /26 is
11111111.11111111.11111111.11000000— twenty-six 1s. - The network address is your IP with every host bit set to 0.
- The broadcast address is your IP with every host bit set to 1.
- A wildcard mask is the mask with every bit flipped.
- Supernetting and route summarisation are about finding the bits that several networks have in common.
Every one of those is obvious in binary and mysterious in decimal. That is why it is worth the hour.
The only table you need to memorise
Each octet is 8 bits, and each bit position has a value:
| Bit position | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
|---|---|---|---|---|---|---|---|---|
| Value | 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1 |
To convert decimal → binary, work left to right: does 128 fit into your number? If yes, write 1 and subtract it. If no, write 0. Move to 64. Repeat.
Take 192: 128 fits (remainder 64) → 1. 64 fits (remainder 0) → 1. Everything else is 0. So 192 = 11000000. That is exactly why a /26 mask ends in 192 — two bits borrowed.
To convert binary → decimal, just add the values where there is a 1. 10101100 = 128 + 32 + 8 + 4 = 172. (Recognise it? That is the first octet of the 172.16.0.0/12 private range.)
The eight numbers worth knowing cold
Subnet masks only ever end in one of these values, because a mask is always 1s followed by 0s:
| Decimal | Binary | Bits borrowed |
|---|---|---|
| 128 | 10000000 | 1 |
| 192 | 11000000 | 2 |
| 224 | 11100000 | 3 |
| 240 | 11110000 | 4 |
| 248 | 11111000 | 5 |
| 252 | 11111100 | 6 |
| 254 | 11111110 | 7 |
| 255 | 11111111 | 8 |
Memorise that column. Combined with the block-size method, it is most of what fast subnetting actually is. Then drill it in practice questions.
Frequently asked questions
How do I convert an IP address to binary?
Convert each octet separately using the bit values 128, 64, 32, 16, 8, 4, 2, 1. Work left to right: if the value fits, write 1 and subtract it; otherwise write 0.
Why do network engineers need to know binary?
Because subnet masks, network and broadcast addresses, wildcard masks and route summarisation are all binary operations. They are obvious in binary and confusing in decimal.
What is 192 in binary?
11000000. That is 128 + 64, which is why a /26 subnet mask ends in 192 — two bits have been borrowed for the network portion.
Is this binary converter free?
Yes, free with no signup, and it runs entirely in your browser so nothing is sent to a server.
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