SUBNET CALCULATOR
Subnet calculator, CIDR maths, instantly.
Enter an IPv4 address and CIDR prefix to get the network address, broadcast address, host count and subnet mask. Runs locally in your browser.
Input
Results
Quick reference
| CIDR | Subnet mask | Usable hosts |
|---|---|---|
| /30 | 255.255.255.252 | 2 |
| /29 | 255.255.255.248 | 6 |
| /28 | 255.255.255.240 | 14 |
| /27 | 255.255.255.224 | 30 |
| /26 | 255.255.255.192 | 62 |
| /25 | 255.255.255.128 | 126 |
| /24 | 255.255.255.0 | 254 |
Everything runs locally in your browser
What can this tool do?
Enter any IPv4 address and CIDR prefix length to instantly get that subnet network address, broadcast address, subnet mask and wildcard mask, total addresses and usable host count (network and broadcast addresses subtracted), plus the first and last usable host IPs. The reference table lists common /24 to /30 divisions for quick checking. Useful for exam prep, network planning and troubleshooting — everything runs locally.
FAQ
Why is the usable host count lower than the total?
Each IPv4 subnet reserves two addresses: the network address and the broadcast address. So usable hosts equal total minus two — except /31 and /32, which are point-to-point and host routes and do not subtract.
What does the number after the slash mean?
It is the network prefix length, i.e. how many leading bits belong to the network. A /24 gives subnet mask 255.255.255.0.