How many usable hosts are in a /24?

254. A /24 contains 256 addresses, and the first is the network address while the last is the broadcast address, leaving 254 assignable to hosts.

What is a wildcard mask?

The bitwise inverse of the subnet mask. A /24 has a mask of 255.255.255.0 and a wildcard of 0.0.0.255. Cisco ACLs and some routing configurations expect the wildcard form. Note that a /31 is reported as two usable addresses, following RFC 3021 for point-to-point links, and a /32 as one.

Does this support IPv6?

Not in this calculator, which is IPv4 only and rejects an IPv6 address with an explicit error rather than partially parsing it. The IPv6 Address Tool covers the same ground for IPv6, and the Subnet Planner and IP Range to CIDR Converter accept both families.

Networking / LOCAL TOOL

CIDR Calculator

Calculate IPv4 network, broadcast, mask, and usable address ranges locally.

Runs locally — input is never uploaded

InputAn IPv4 CIDR block, e.g. 192.168.1.0/24

ResultReady when you are

WHAT IT DOES

Every number you need from one IPv4 block.

Enter an IPv4 block such as 192.168.10.0/23 to get the network address, broadcast address, subnet mask, wildcard mask, total address count, and the usable host range. It answers the question that comes up whenever a firewall rule, a VPC subnet, or a route table needs writing.

Why use it?

Use it to check an IPv4 subnet's boundaries before writing a route, firewall rule, or address allocation.

How to use this tool

Enter an IPv4 address with its prefix, such as 192.168.10.37/24, and calculate.
Read the derived network, broadcast, and usable range. In this example the network is 192.168.10.0/24, not a block starting at .37.
Copy the field required by your destination: a subnet mask and wildcard mask are inverses, not interchangeable labels. Check /31 and /32 results as special cases.

Details and limitations

Prefix lengths from /0 to /32 are supported, including the /31 point-to-point and /32 single-host cases.
Both the subnet mask and its inverted wildcard mask are shown, because ACLs frequently want the latter.
Usable host counts exclude the network and broadcast addresses for prefixes shorter than /31.
A host address with a prefix, such as 10.0.4.37/20, is accepted and its containing network is derived.

WORKED EXAMPLES

A host address is not the subnet boundary

Calculate the block containing the given host. Use the derived network when your firewall or router expects a network prefix.

IPv4 with prefix

192.168.10.37/24

Expected result

Network 192.168.10.0, broadcast 192.168.10.255, mask 255.255.255.0, and 254 usable addresses from .1 through .254. The host's .37 does not move the block boundary.

COMMON QUESTIONS

CIDR Calculator questions

How many usable hosts are in a /24?: 254. A /24 contains 256 addresses, and the first is the network address while the last is the broadcast address, leaving 254 assignable to hosts.
What is a wildcard mask?: The bitwise inverse of the subnet mask. A /24 has a mask of 255.255.255.0 and a wildcard of 0.0.0.255. Cisco ACLs and some routing configurations expect the wildcard form. Note that a /31 is reported as two usable addresses, following RFC 3021 for point-to-point links, and a /32 as one.
Does this support IPv6?: Not in this calculator, which is IPv4 only and rejects an IPv6 address with an explicit error rather than partially parsing it. The IPv6 Address Tool covers the same ground for IPv6, and the Subnet Planner and IP Range to CIDR Converter accept both families.