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IPv4 Subnet Calculator

Enter an address and a prefix or mask. Get the network and broadcast addresses, the usable host range, the masks and the binary behind them, then split the block into subnets.

Last updated November 6, 2026

IP addressOr type it with its prefix, e.g. 10.0.0.5/16Prefix and subnet maskHosts you need (optional)We’ll suggest the smallest subnet that fits

Network address: 192.168.10.64
Broadcast address: 192.168.10.127
First usable host: 192.168.10.65
Last usable host: 192.168.10.126
Usable hosts: 62
Total addresses: 64
Subnet mask: 255.255.255.192
Wildcard mask: 0.0.0.63
CIDR notation: 192.168.10.64/26
Address type: Private
Address class: Class C
Host bits: 6 of 32

In binary

Network bitsHost bits

Address	11000000.10101000.00001010.01001101	192.168.10.77
Mask	11111111.11111111.11111111.11000000	255.255.255.192
Network	11000000.10101000.00001010.01000000	192.168.10.64
Broadcast	11000000.10101000.00001010.01111111	192.168.10.127

Split this network

4 subnets of /28, 14 usable hosts each

Into

#	Network	Usable range	Broadcast
1	192.168.10.64/28	192.168.10.65 – 192.168.10.78	192.168.10.79
2	192.168.10.80/28	192.168.10.81 – 192.168.10.94	192.168.10.95
3	192.168.10.96/28	192.168.10.97 – 192.168.10.110	192.168.10.111
4	192.168.10.112/28	192.168.10.113 – 192.168.10.126	192.168.10.127

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Guide

How to read your results

Network and broadcast

The network address is the first address in the block, with every host bit set to 0. It names the subnet and can’t be given to a device.

The broadcast address is the last one, with every host bit set to 1. A packet sent there reaches every host on the subnet.

Usable hosts

Usable hosts are everything between the two: 2^(host bits) − 2. A /26 has 6 host bits, so 64 addresses and 62 usable hosts.

Two exceptions: a /31 gives two usable addresses for point-to-point links (RFC 3021), and a /32 is a single host.

Subnet mask and wildcard mask

The subnet mask is the prefix written in dotted decimal: /26 is 255.255.255.192.

The wildcard mask is its inverse (0.0.0.63 for a /26). Cisco access control lists and OSPF network statements use it.

Splitting a network

Each bit you add to the prefix doubles the number of subnets and halves the size of each one. Splitting a /24 into /26s gives four subnets of 62 usable hosts.

Need a subnet for a number of hosts? Type it into “Hosts you need” and the calculator picks the smallest prefix that fits.

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FAQs

Got Questions? We’ve Got Answers.

Find quick answers or contact our support team.

How do I calculate a subnet by hand?

Find the block size: 256 minus the mask’s value in the interesting octet (the one that isn’t 255 or 0). The network is the multiple of the block size at or below the address in that octet; the broadcast is one less than the next multiple. Our Subnetting Practice tool walks through it step by step.

What is the difference between a subnet mask and a prefix?

They say the same thing in two ways. A prefix like /24 counts the network bits; the mask 255.255.255.0 writes those 24 ones in dotted decimal.

Why do I lose two addresses in every subnet?

The first address identifies the network and the last is the broadcast address, so neither can be assigned to a host. Point-to-point /31 links and single-host /32s are the exceptions.

Which addresses are private?

10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16 (RFC 1918). The calculator also flags loopback (127.0.0.0/8), APIPA link-local (169.254.0.0/16), carrier-grade NAT (100.64.0.0/10) and multicast addresses.

Does the calculator send my data anywhere?

No. Everything is worked out in your browser.