IP Subnet Calculator

Enter any IPv4 address and CIDR prefix and get the complete subnet picture: network and broadcast addresses, subnet mask and wildcard, first and last usable host, host counts, address class — plus the mask in binary so you can see where the network bits end.

Runs locally — nothing you enter is sent Calculators Free · no signup

How to use

Enter an IPv4 address (e.g. 192.168.1.10).
Enter the CIDR prefix length (e.g. 24 for /24, i.e. 255.255.255.0).
Press Calculate and read the full subnet breakdown, including the binary mask.

Examples

Input

192.168.1.10 /26

Network · Broadcast

192.168.1.0 · 192.168.1.63

Usable range

192.168.1.1 — 192.168.1.62 (62 hosts)

Supported formats

IPv4 dotted-quad addresses with CIDR prefixes /0 through /32.
/31 (point-to-point, RFC 3021) and /32 (single host) edge cases handled correctly.

Privacy

This tool runs entirely in your browser. Nothing you enter or open is sent anywhere. Privacy policy.

Limitations

IPv4 only — use the IPv6 Subnet Calculator for IPv6 prefixes.
It computes the subnet containing the given address; to plan several subnets of different sizes, use the VLSM Calculator.

FAQ

How many usable hosts are in a /24?

254. A /24 has 2⁸ = 256 addresses, minus the network and broadcast addresses. In general usable hosts = 2^(32−prefix) − 2.

What is a wildcard mask?

The inverse of the subnet mask (255.255.255.0 → 0.0.0.255), used in Cisco ACLs and OSPF statements. This calculator shows it for every subnet.

Why does /31 show 2 usable hosts?

RFC 3021 allows /31 subnets on point-to-point links with no network/broadcast reservation — both addresses are usable. Standard subnets subtract two.