Toolkeel

IP subnet calculator

Work out network ranges for firewalls, VPNs, cloud VPCs and home networks from CIDR notation or an address and mask.

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How to use it

  1. Enter an address with a prefix (10.0.0.5/24) or with a mask (10.0.0.5 255.255.255.0).

  2. Read the network, broadcast, host range and counts.

  3. Copy any value.

About this tool

CIDR notation such as 192.168.1.0/24 means the first 24 bits are the network and the remaining 8 identify hosts, giving 256 addresses, of which 254 are usable (the first is the network address and the last is the broadcast address). For /31 and /32 networks, all addresses are usable, as defined for point-to-point links.

Private ranges (RFC 1918) are 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16. Cloud providers often reserve a few addresses per subnet, so check your provider's documentation.

Good to know

  • IPv4 only.
  • Cloud platforms may reserve extra addresses in each subnet.

Frequently asked questions

How many hosts are in a /24?

256 addresses, 254 usable hosts.

What is a wildcard mask?

The inverse of the subnet mask (for /24: 0.0.0.255), used in some router and firewall rules.

Is 172.20.0.1 a private address?

Yes. It is inside 172.16.0.0/12, one of the three private ranges.

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Last updated 2026-10-20 by the Toolkeel team. How we build and check our tools.