Calculate CIDR

Calculate network boundaries, host counts, and masks from a CIDR prefix.

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ToolCIDR Calculator
Input
Output
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Preview

How it works

Address and prefix become fixed-width bits; the mask yields network and broadcast boundaries, host count, wildcard mask, and range. IPv4 and IPv6 use separate widths and special-address rules.

  • Prefix length expresses routing boundaries compactly.
  • Host counts follow the selected address family.

Worked example

Calculate a /24 private subnet
Get network, broadcast, mask, and range for 192.168.1.0/24
Input
											192.168.1.0/24
Output
												CIDR: 192.168.1.0/24
Network address: 192.168.1.0
Broadcast address: 192.168.1.255
First IP: 192.168.1.0
Last IP: 192.168.1.255
Total addresses: 256
Subnet mask: 255.255.255.0
Wildcard mask: 0.0.0.255

When to use this

Routers, firewalls, and IPAM systems calculate CIDR blocks.

Edge cases

  • A host-bit input is normalized to its network.
  • /31 and /32 have special IPv4 semantics.
  • IPv6 has no broadcast and needs different host rules.

References