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IP / CIDR calculator

Find network boundaries and exact address counts.

How to use ↓

IPv4: /0–32 · IPv6: /0–128. Domains, ports, zone IDs and dotted-decimal masks are not supported.

No IP lookup or connection is made. Inputs and results are not saved or uploaded.

QUICK GUIDE

Find network boundaries with CIDR.

Enter an IP and its prefix length after /. Host bits are cleared to find the network start. Large IPv6 address counts use exact integer arithmetic.

  1. 01

    Enter an address and prefix

    Enter an address such as 192.168.1.10/24 or 2001:db8::1/64. Compressed IPv6 and a trailing IPv4 component are supported.

  2. 02

    Check the range and membership

    Optionally enter an IP of the same address family to check membership. The tool calculates ranges; it never contacts network devices.

  3. 03

    Review the assumptions

    Address counts do not mean assignable or Internet-reachable devices. Check reserved addresses and any extra restrictions imposed by your cloud provider or equipment.

192.168.1.10/24

192.168.1.0/24
255.255.255.0
192.168.1.0 → 192.168.1.255
256 addresses

References: RFC 3021 · RFC 4291 · RFC 5952

Frequently asked questions

How are /31 and /32 handled?

IPv4 /0–30 displays the conventional host range excluding its first and last addresses. /31 assumes two point-to-point endpoints; /32 is one address. Neither displays a separate broadcast address.

Why is there no IPv6 host count?

IPv6 has no broadcast. We show the full address range and count, not a claim about assignable hosts. IPv6 with an embedded IPv4 address is also displayed in compressed hexadecimal form.