Free Subnet Calculator (IPv4 / CIDR)

Enter an IPv4 address and prefix to get the network, broadcast, usable host range, masks, and a network-vs-host binary view.

Private (RFC 1918)Class C
Network address192.168.1.0/24
Broadcast address192.168.1.255
Usable host range192.168.1.1 – 192.168.1.254
Usable hosts254
Total addresses256
Subnet mask255.255.255.0
Wildcard mask0.0.0.255
Address11000000.10101000.00000001.00001010
Mask11111111.11111111.11111111.00000000

Network bits · host bits

How to use / FAQ

Enter any IPv4 address — or paste full CIDR notation like 10.0.0.1/16 and the prefix sets itself — then pick the prefix or mask. You get the network and broadcast addresses, the usable host range and count, wildcard mask, and a binary view that shows exactly where the network bits end and the host bits begin.

What does the /24 in CIDR notation mean?

The number of leading bits that identify the network — the rest identify hosts inside it. /24 means 24 network bits and 8 host bits: 256 addresses, of which 254 are usable. Each step smaller doubles the network: /23 has 510 usable hosts, /22 has 1,022.

Why are two addresses missing from the usable count?

The all-zeros host address names the network itself and the all-ones address is the broadcast address — neither can be assigned to a device. That's why a /24 has 254 usable hosts, not 256. The exceptions are /31 (both addresses usable on point-to-point links, per RFC 3021) and /32 (a single host route).

What's the difference between a subnet mask and a wildcard mask?

They're bit-for-bit inverses. The subnet mask (255.255.255.0) marks the network bits with ones; the wildcard mask (0.0.0.255) marks the host bits with ones. Wildcard masks appear mainly in Cisco access-control lists and OSPF configuration.

What are the private (RFC 1918) ranges?

10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 — addresses reserved for use inside local networks, never routed on the public internet. The tool also flags loopback (127/8), link-local (169.254/16), carrier-grade NAT (100.64/10), and multicast (224/4) addresses.

Does this work for IPv6?

Not yet — this calculator is IPv4-only. IPv6's 128-bit space works differently enough (no broadcast, standard /64 subnets) that it deserves its own tool.