IP subnet calculator (IPv4, CIDR)
192.168.1.10/24 is in the network 192.168.1.0, mask 255.255.255.0: 256 addresses, 254 of which can be given to devices, from 192.168.1.1 to 192.168.1.254.
- Checked on thousands of cases
- Sources: RFC 4632, RFC 1122, RFC 3021, RFC 1918
- Updated November 6, 2026
Usable addresses
Devices from 192.168.1.1 to 192.168.1.254
Network
Subnet mask
Broadcast
Wildcard mask
Total addresses
Private address (RFC 1918 block 192.168.0.0/16).
Quick challenge
Streak 0Best 0
Test yourself: every answer is computed by the tool, and the wrong choices are the most common traps.
How it works
Formula: Usable addresses = 2^(32 − prefix) − 2
The prefix says how many of the 32 bits identify the network (RFC 4632); the remaining bits number the hosts. A /24 leaves 8 host bits, so 2⁸ = 256 addresses. The network address has every host bit at 0 and the broadcast address every host bit at 1: neither can be given to a device (RFC 1122), which leaves 254. Two exceptions: on a point-to-point link, a /31 uses both of its addresses (RFC 3021), and a /32 is a single address.
Worked examples
192.168.1.10/24
Network 192.168.1.0, devices from 192.168.1.1 to 192.168.1.254: 254 usable addresses.
A /8 such as 10.0.0.0/8
16,777,214 usable addresses, mask 255.0.0.0.
A /26
62 usable addresses: a quarter of a /24.
Common mistakes
Counting 256 devices in a /24.
The network and broadcast addresses are reserved: 254.
Mistaking the mask 255.255.255.0 for a /8.
255.255.255.0 has 24 bits set to 1: it is a /24. A /8 is 255.0.0.0.
Thinking every 172.x address is private.
The private block 172.16.0.0/12 ends at 172.31.255.255: 172.32.0.1 is public.
Subnet size by prefix
| Prefix | Mask | Addresses | Usable |
|---|---|---|---|
| /8 | 255.0.0.0 | 16,777,216 | 16,777,214 |
| /16 | 255.255.0.0 | 65,536 | 65,534 |
| /20 | 255.255.240.0 | 4,096 | 4,094 |
| /22 | 255.255.252.0 | 1,024 | 1,022 |
| /23 | 255.255.254.0 | 512 | 510 |
| /24 | 255.255.255.0 | 256 | 254 |
| /25 | 255.255.255.128 | 128 | 126 |
| /26 | 255.255.255.192 | 64 | 62 |
| /27 | 255.255.255.224 | 32 | 30 |
| /28 | 255.255.255.240 | 16 | 14 |
| /29 | 255.255.255.248 | 8 | 6 |
| /30 | 255.255.255.252 | 4 | 2 |
| /31 | 255.255.255.254 | 2 | 2 |
| /32 | 255.255.255.255 | 1 | 1 |
Frequently asked questions
How many devices fit in a /24?
254: a /24 holds 256 addresses, minus the network address (.0) and the broadcast address (.255).
What is the difference between a prefix and a mask?
They say the same thing two ways. /24 means the first 24 bits are 1, written 255.255.255.0 as a mask; /16 is 255.255.0.0 and /20 is 255.255.240.0.
Which IP addresses are private?
RFC 1918 sets aside three blocks for private networks: 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16. They are not routed on the Internet, which is why home routers use them.