IP Subnet Calculator
Enter an IPv4 address with its prefix (CIDR), such as 192.168.10.37/26.
Subnetting basics
An IPv4 address has 32 bits. The prefix (/26) says how many of them identify the network, and the rest identify hosts. A /26 leaves 6 host bits: 2⁶ = 64 addresses, of which 62 are usable, because the first is the network address and the last is the broadcast address. /31 and /32 are special cases used for point-to-point links and single hosts.
Common prefixes
- /24 — 255.255.255.0 — 254 hosts (a typical home or office LAN)
- /16 — 255.255.0.0 — 65,534 hosts
- /30 — 4 addresses, 2 hosts (router links)
The wildcard mask (the inverse of the subnet mask) is used in Cisco ACLs and OSPF. The tool also says whether the address is private (10.x, 172.16–31.x, 192.168.x), carrier-grade NAT (100.64/10, used by many ISPs), loopback, link-local or public. It is useful for CCNA study, router and firewall setup, and cloud network design. IPv6 is not covered.
How it works
- Enter — type or paste your values or text.
- Get the result — it is worked out in your browser.
- Adjust — change the inputs to compare, or copy the result.
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