Other

Subnet Calculator

Calculate network address, mask, broadcast, host range, and usable host count.

Inputs

Results update as you edit.

IP address

CIDR prefix

Network address

192.168.1.0/24

Results update as the calculator inputs change.

Subnet mask

255.255.255.0

Broadcast

192.168.1.255

First usable

192.168.1.1

Last usable

192.168.1.254

Usable hosts

254

How to Calculate an IPv4 Subnet

IP Address

The IP address is combined with the prefix to identify the subnet.

CIDR Prefix

The prefix length determines how many bits are network bits versus host bits.

Host Range

Network and broadcast addresses define the usable host range.

How to Read Subnet Results

A subnet calculator converts an IPv4 address and CIDR prefix into network address, subnet mask, broadcast address, usable host range, and address count.

What Affects a Subnet?

IPv4 Address

The entered address is located inside a calculated network block.

Prefix Length

A smaller prefix creates more host addresses; a larger prefix creates smaller subnets.

Network Address

The first address identifies the subnet and is not normally assigned to a host.

Broadcast Address

The last address is traditionally reserved for broadcast in many IPv4 networks.

Usable Hosts

Usable host count excludes reserved addresses in typical subnets.

Subnet Size

Choosing a subnet size balances growth room and address efficiency.

Common Subnet Uses

CIDR to Mask

Convert prefix length into dotted-decimal subnet mask.

Host Planning

Find first and last usable host addresses.

Network Design

Split address space into blocks for routing or segmentation.

Frequently Asked Questions

What does CIDR mean?

CIDR notation uses a slash and prefix length, such as /24, to show how many bits are used for the network.

What is a subnet mask?

A subnet mask marks which bits belong to the network portion of an IPv4 address.

Why are network and broadcast addresses excluded?

In many IPv4 subnets, the first address identifies the network and the last is reserved for broadcast.

How many hosts are in a /24?

A typical /24 has 256 total addresses and 254 usable host addresses.

Does this support IPv6?

No. This calculator focuses on IPv4 subnetting.