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Subnet / CIDR Calculator

Calculate network address, broadcast, usable IP range, subnet mask, and wildcard from any CIDR notation.

Frequently Asked Questions

Common questions about the Subnet / CIDR Calculator tool.

CIDR (Classless Inter-Domain Routing) expresses a network range as `IP/prefix` — e.g. `10.0.0.0/24` means the first 24 bits are the network, last 8 bits are host. /24 gives 256 addresses (254 usable).

Match subnet size to host count + 30-50% headroom. /30 (2 hosts) = point-to-point links. /27 (30 hosts) = small office LAN. /24 (254 hosts) = typical department LAN. /22 (1,022 hosts) = campus.

In `10.0.0.0/24`: .0 is the network address, .255 is the broadcast address — both reserved. .1 through .254 (254 IPs) are usable for hosts. Common practice: .1 for the default gateway.

A /31 is a 2-address subnet used for point-to-point links (RFC 3021). Both addresses are usable — no network/broadcast reservation. Great for WAN links between routers.

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