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About the IPv4 Lookup & CIDR Calculator

Inspect an IPv4 address or work out a subnet: given a CIDR block you get the network address, broadcast address, usable host range and the total address count.

• CIDR to range, mask and host count
• Address class and reserved-range detection
• Useful for firewall rules and allowlists

Frequently asked questions

How many hosts are in a /24?

256 addresses, of which 254 are usable — the first is the network address and the last is the broadcast address.

What does the /number in CIDR mean?

It is the count of leading bits that identify the network. A larger number means a smaller subnet.

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