Subnet Calculator
Enter any IPv4 address in CIDR notation to get the network and broadcast addresses, usable host range, subnet mask, wildcard mask and host count.
A subnet calculator takes an IPv4 address in CIDR notation and returns the network and broadcast addresses, the usable host range, the subnet mask, the wildcard mask and the host count. Enter something like 192.168.1.0/24 and every derived value is computed at once.
Runs entirely in your browser · no signup · nothing is uploaded · updated 2026-08-29
- Network address
- 192.168.1.0
- Broadcast address
- 192.168.1.255
- First usable host
- 192.168.1.1
- Last usable host
- 192.168.1.254
- Subnet mask
- 255.255.255.0
- Wildcard mask
- 0.0.0.255
- Usable hosts
- 254
- Total addresses
- 256
- Prefix
- /24
How to use it
- 1.Enter an address in CIDR form, such as 192.168.1.0/24.
- 2.Read the network, broadcast and usable host range.
- 3.Use the wildcard mask when writing ACLs - it is the inverse of the subnet mask.
CIDR prefix table
Usable hosts is 2^(32-prefix) - 2, because the first address names the network and the last is the broadcast address.
| Prefix | Subnet mask | Addresses | Usable hosts |
|---|---|---|---|
| /32 | 255.255.255.255 | 1 | 1 (host route) |
| /31 | 255.255.255.254 | 2 | 2 (point-to-point) |
| /30 | 255.255.255.252 | 4 | 2 |
| /29 | 255.255.255.248 | 8 | 6 |
| /28 | 255.255.255.240 | 16 | 14 |
| /27 | 255.255.255.224 | 32 | 30 |
| /26 | 255.255.255.192 | 64 | 62 |
| /25 | 255.255.255.128 | 128 | 126 |
| /24 | 255.255.255.0 | 256 | 254 |
| /23 | 255.255.254.0 | 512 | 510 |
| /22 | 255.255.252.0 | 1,024 | 1,022 |
| /20 | 255.255.240.0 | 4,096 | 4,094 |
| /16 | 255.255.0.0 | 65,536 | 65,534 |
| /8 | 255.0.0.0 | 16,777,216 | 16,777,214 |
Frequently asked questions
Why are two addresses unusable?
The first is the network address and the last is the broadcast address. Neither can be assigned to a host, which is why a /24 gives 254 usable addresses rather than 256.
What about /31 and /32?
A /32 is a single host route. A /31 is a special case defined for point-to-point links where both addresses are usable, since there is no need for a broadcast address.
What is a wildcard mask?
The bitwise inverse of the subnet mask. Cisco ACLs and OSPF use it instead of a subnet mask, so /24 is 0.0.0.255 rather than 255.255.255.0.
Which ranges are private?
10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16 are private. 100.64.0.0/10 is carrier-grade NAT, and 169.254.0.0/16 is link-local.
How many hosts are in a /24?
254 usable. A /24 spans 256 addresses, minus the network address and the broadcast address. The general formula is 2^(32-prefix) - 2.
What does /24 actually mean?
The first 24 bits are the network portion, leaving 8 bits for hosts. It is the same information as the mask 255.255.255.0, written more compactly.
How do I split a network into smaller subnets?
Borrow bits from the host portion. Splitting a /24 into four means moving to /26, giving 64 addresses and 62 usable hosts each.
How is IPv6 subnetting different?
There is no broadcast address and no scarcity. A /64 is the standard size for any single network regardless of how many devices it holds, and you subnet by taking prefixes shorter than /64.
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