Quick reference
IPv4 subnet cheat sheet
CIDR prefixes from /0 through /32 with subnet masks, wildcard masks, address counts, and contextual /31 and /32 behavior.
Ready reference
Every IPv4 prefix in one auditable table.
Address counts come from the same tested IPv4 engine as the calculator. Traditional subnets reserve network and broadcast addresses; `/31` and `/32` use their operational point-to-point and host-route meanings.
Open the IPv4 calculatorCIDR table
Masks, wildcards, and capacity
Wildcard masks are the bitwise inverse of subnet masks. Counts use modern `/31` and `/32` semantics rather than subtracting two from every block.
| CIDR | Subnet mask | Wildcard mask | Total | Usable | Host behavior |
|---|---|---|---|---|---|
/0 | 0.0.0.0 | 255.255.255.255 | 4,294,967,296 | 4,294,967,294 | Network + broadcast reserved |
/1 | 128.0.0.0 | 127.255.255.255 | 2,147,483,648 | 2,147,483,646 | Network + broadcast reserved |
/2 | 192.0.0.0 | 63.255.255.255 | 1,073,741,824 | 1,073,741,822 | Network + broadcast reserved |
/3 | 224.0.0.0 | 31.255.255.255 | 536,870,912 | 536,870,910 | Network + broadcast reserved |
/4 | 240.0.0.0 | 15.255.255.255 | 268,435,456 | 268,435,454 | Network + broadcast reserved |
/5 | 248.0.0.0 | 7.255.255.255 | 134,217,728 | 134,217,726 | Network + broadcast reserved |
/6 | 252.0.0.0 | 3.255.255.255 | 67,108,864 | 67,108,862 | Network + broadcast reserved |
/7 | 254.0.0.0 | 1.255.255.255 | 33,554,432 | 33,554,430 | Network + broadcast reserved |
/8 | 255.0.0.0 | 0.255.255.255 | 16,777,216 | 16,777,214 | Network + broadcast reserved |
/9 | 255.128.0.0 | 0.127.255.255 | 8,388,608 | 8,388,606 | Network + broadcast reserved |
/10 | 255.192.0.0 | 0.63.255.255 | 4,194,304 | 4,194,302 | Network + broadcast reserved |
/11 | 255.224.0.0 | 0.31.255.255 | 2,097,152 | 2,097,150 | Network + broadcast reserved |
/12 | 255.240.0.0 | 0.15.255.255 | 1,048,576 | 1,048,574 | Network + broadcast reserved |
/13 | 255.248.0.0 | 0.7.255.255 | 524,288 | 524,286 | Network + broadcast reserved |
/14 | 255.252.0.0 | 0.3.255.255 | 262,144 | 262,142 | Network + broadcast reserved |
/15 | 255.254.0.0 | 0.1.255.255 | 131,072 | 131,070 | Network + broadcast reserved |
/16 | 255.255.0.0 | 0.0.255.255 | 65,536 | 65,534 | Network + broadcast reserved |
/17 | 255.255.128.0 | 0.0.127.255 | 32,768 | 32,766 | Network + broadcast reserved |
/18 | 255.255.192.0 | 0.0.63.255 | 16,384 | 16,382 | Network + broadcast reserved |
/19 | 255.255.224.0 | 0.0.31.255 | 8,192 | 8,190 | Network + broadcast reserved |
/20 | 255.255.240.0 | 0.0.15.255 | 4,096 | 4,094 | Network + broadcast reserved |
/21 | 255.255.248.0 | 0.0.7.255 | 2,048 | 2,046 | Network + broadcast reserved |
/22 | 255.255.252.0 | 0.0.3.255 | 1,024 | 1,022 | Network + broadcast reserved |
/23 | 255.255.254.0 | 0.0.1.255 | 512 | 510 | Network + broadcast reserved |
/24 | 255.255.255.0 | 0.0.0.255 | 256 | 254 | Network + broadcast reserved |
/25 | 255.255.255.128 | 0.0.0.127 | 128 | 126 | Network + broadcast reserved |
/26 | 255.255.255.192 | 0.0.0.63 | 64 | 62 | Network + broadcast reserved |
/27 | 255.255.255.224 | 0.0.0.31 | 32 | 30 | Network + broadcast reserved |
/28 | 255.255.255.240 | 0.0.0.15 | 16 | 14 | Network + broadcast reserved |
/29 | 255.255.255.248 | 0.0.0.7 | 8 | 6 | Network + broadcast reserved |
/30 | 255.255.255.252 | 0.0.0.3 | 4 | 2 | Network + broadcast reserved |
/31 | 255.255.255.254 | 0.0.0.1 | 2 | 2 | 2 endpoints |
/32 | 255.255.255.255 | 0.0.0.0 | 1 | 1 | 1 host route |
Reading the table
Three rules prevent the common mistakes.
Traditional `/0` through `/30`
The first address is the network address and the last is the broadcast address. The usable count is the block size minus two.
Point-to-point `/31`
RFC 3021 uses both addresses as endpoints. There is no network-or-broadcast subtraction in this context.
Host-route `/32`
The one address is the complete route. It is both the start and end of the range and has no separate broadcast address.