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IP Subnet Calculator

Enter an IPv4 address with a CIDR prefix or subnet mask and instantly see the network, broadcast, host range, usable hosts and binary breakdown.

Try:

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 host range

192.168.1.1 - 192.168.1.254

CIDR notation

192.168.1.0/24

Total hosts

256

Usable hosts

254

Class

C

Type

Private

Network address (binary)

11000000.10101000.00000001.00000000

Subnet mask (binary)

11111111.11111111.11111111.00000000

Runs entirely in your browser session — nothing is sent anywhere, no account needed.

Common subnet examples

CIDR Subnet mask Usable hosts
/24 255.255.255.0 254
/30 255.255.255.252 2
/29 255.255.255.248 6
/16 255.255.0.0 65,534
/8 255.0.0.0 16,777,214

How subnetting works

An IPv4 address is 32 bits split into a network part and a host part. The subnet mask (or CIDR prefix like /24) decides where that split happens: the prefix counts how many leading bits identify the network, and the rest identify hosts inside it.

The first address in a block is the network address and the last is the broadcast address — neither can be assigned to a device, which is why a /24 has 256 total addresses but only 254 usable hosts. The wildcard mask is the inverse of the subnet mask and is often used in ACLs and routing rules.

Smaller prefixes (e.g. /16, /8) cover more hosts; larger prefixes (e.g. /30, /31) carve a network into tiny segments. A /31 is reserved for point-to-point links and a /32 identifies a single host.

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Frequently asked questions

What is a subnet calculator?
A subnet calculator takes an IP address and a subnet mask or CIDR prefix and works out the network address, broadcast address, usable host range and number of hosts — saving you from doing the binary maths by hand.
What's the difference between a /24 and a /16?
A /24 reserves 24 bits for the network, leaving 8 bits (254 usable hosts). A /16 reserves only 16 bits, leaving 16 bits for hosts (65,534 usable). The smaller the prefix number, the larger the network.
How many usable hosts are in a subnet?
For prefixes up to /30 it's 2^(32 − prefix) − 2, because the network and broadcast addresses are reserved. A /31 (point-to-point, RFC 3021) and a /32 are special cases with no reserved addresses.
What is a wildcard mask?
The wildcard mask is the bitwise inverse of the subnet mask (for /24 it's 0.0.0.255). It's used in access control lists and routing protocols like OSPF to match ranges of addresses.
Is this calculator free and private?
Yes. It's completely free, needs no account, and the calculation happens within your session — your addresses aren't stored or shared.