IP Subnet Calculator
Network, broadcast, host range, and masks from any IPv4 address and CIDR prefix
Tip: paste 10.0.0.5/16 to set both fields at once
Results for 192.168.1.10/24
Binary Representation
Blue = network portion (24 bits), gray = host portion (8 bits)
CIDR ↔ Netmask Quick Table
Click a row to use that prefix.
| CIDR | Netmask | Total addresses | Usable hosts |
|---|---|---|---|
| /8 | 255.0.0.0 | 16,777,216 | 16,777,214 |
| /9 | 255.128.0.0 | 8,388,608 | 8,388,606 |
| /10 | 255.192.0.0 | 4,194,304 | 4,194,302 |
| /11 | 255.224.0.0 | 2,097,152 | 2,097,150 |
| /12 | 255.240.0.0 | 1,048,576 | 1,048,574 |
| /13 | 255.248.0.0 | 524,288 | 524,286 |
| /14 | 255.252.0.0 | 262,144 | 262,142 |
| /15 | 255.254.0.0 | 131,072 | 131,070 |
| /16 | 255.255.0.0 | 65,536 | 65,534 |
| /17 | 255.255.128.0 | 32,768 | 32,766 |
| /18 | 255.255.192.0 | 16,384 | 16,382 |
| /19 | 255.255.224.0 | 8,192 | 8,190 |
| /20 | 255.255.240.0 | 4,096 | 4,094 |
| /21 | 255.255.248.0 | 2,048 | 2,046 |
| /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 |
How IPv4 subnetting works
An IPv4 address is a 32-bit number written as four octets (192.168.1.10). CIDR notation appends a prefix length — /24 means the first 24 bits identify the network and the remaining 8 bits identify hosts within it. The subnet mask is the same idea written as an address: /24 = 255.255.255.0, because the first 24 bits are ones.
The network address is computed with a bitwise AND between the IP and the mask (192.168.1.10 AND 255.255.255.0 = 192.168.1.0). The broadcast address sets every host bit to one (192.168.1.255). Everything between them is the usable host range: 192.168.1.1 through 192.168.1.254, which is 2⁸ − 2 = 254 hosts. The wildcard mask is simply the inverted subnet mask (0.0.0.255) and is used in Cisco ACLs and OSPF configuration.
Each time you add one bit to the prefix you halve the subnet: a /24 has 254 usable hosts, a /25 has 126, a /26 has 62, and a /30 (common on router links) has just 2. Two special cases: a /31 (RFC 3021) uses both of its addresses on point-to-point links, and a /32 denotes a single host. Private ranges reserved by RFC 1918 — 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 — are never routed on the public internet.
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