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IP Range Calculator

Usable host ranges

IP Range Calculator

First IP—
Last IP—
Total IPs—
Usable IPs—
CIDR—

CIDR Blocks

CIDRNetworkBroadcastUsable Hosts

How to use the ip range calculator

  1. Enter a network and prefix. The tool returns the first and last usable host plus the total addresses.
  2. Special cases: /31 follows RFC 3021 (both addresses are usable), /32 is a single host.
  3. Use the output to plan DHCP scope size or static IP allocation.

Frequently asked questions

How is the usable host range different from total addresses?

Total addresses is the full size of the subnet (2^(32-N) for IPv4). Usable range excludes the network and broadcast, which are reserved.

Why does a /30 have only 2 usable hosts?

A /30 has 4 addresses total. The network and broadcast are reserved, leaving 2 — exactly what you need for one router-to-router point-to-point link.

Can the broadcast address be assigned to a host?

Not in classic IPv4. RFC 3021 changes this for /31 prefixes only: on a /31 both addresses are usable as host addresses.

How do /31 RFC 3021 ranges differ from classic /30?

A /31 has 2 addresses, both usable. A /30 has 4 with 2 usable. /31 saves two addresses on every point-to-point link, which adds up across large networks.