IPv4 Address CIDR Prefix

Result

Network

Broadcast

Subnet mask

Wildcard mask

Usable hosts

Address type

First host

Last host

Total addresses

Input IP is network address Input IP is broadcast address

CIDR calculation checklist

Calculate network address, broadcast address, and usable IPv4 host ranges before changing firewall or subnet settings.

See the actual start and end addresses for CIDR blocks such as 10.0.0.0/24.

Check whether a firewall, allowlist, or VPN range is broader or narrower than intended before deployment.

Record network address, broadcast address, and host count to make infrastructure notes clearer.

How to use it

Enter the IPv4 address and prefix length in CIDR notation.

Review the calculated network, broadcast, and host range values.

Compare the result with the range needed by your allowlist or route rule.

Apply cloud-provider reserved-address rules separately when relevant.

Real input and output

Input

192.168.0.0/24

Output

Network 192.168.0.0
Broadcast 192.168.0.255
Host range 192.168.0.1 - 192.168.0.254
Usable hosts 254

Input

10.0.8.0/22

Output

Network 10.0.8.0
Broadcast 10.0.11.255
Host range 10.0.8.1 - 10.0.11.254
Usable hosts 1,022

Errors you will hit

Usable hosts exclude the network address and the broadcast address. A /24 gives 254 usable hosts, not 256.

A /32 identifies a single host. A /31 is used for point-to-point router links and uses both addresses with no broadcast (RFC 3021).

A /26 is smaller than a /24. As the number grows the host count shrinks — a common inversion when writing firewall or security group rules.

Things to check

This tool focuses on IPv4 CIDR calculation. IPv6 uses different notation and sizing rules.

Cloud networks may reserve some addresses in every subnet. Confirm usable host counts with the platform documentation.

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