Network tool

CIDR calculator

Enter an IPv4 or IPv6 CIDR network. Host-prefix input such as 8.8.8.8/24 is accepted and normalized to the canonical network.

Normalized 8.8.8.8/24 to the canonical network 8.8.8.0/24.

Input: 8.8.8.8/24
Canonical network: 8.8.8.0/24
IP version: IPv4
Prefix length: 24
Network address: 8.8.8.0
First address: 8.8.8.0
Last address: 8.8.8.255
Total addresses: 256
Netmask: 255.255.255.0
Broadcast: 8.8.8.255
Usable hosts: 254

Reference

Output fields

Canonical network: The normalized CIDR block after host bits are cleared, such as 8.8.8.0/24.
First and last address: The full inclusive range covered by the prefix.
Total addresses: The number of IPv4 or IPv6 addresses in the block.
Netmask and broadcast: IPv4 compatibility fields. IPv6 uses prefix lengths instead.

Overview

What this tool does

The CIDR calculator normalizes a network, calculates its first and last address, counts total addresses, and shows IPv4-specific netmask, broadcast, and usable host values.

Use it when a firewall, DNS provider, hosting panel, or network document gives you CIDR notation and you need the actual address range. Start with the CIDR notation guide if the slash number is unfamiliar.

Examples

Example inputs

Host-prefix IPv4

8.8.8.8/24 Normalizes to 8.8.8.0/24 and shows the full 256-address range. Calculate 8.8.8.8/24

IPv6 network

2001:db8::/32 Shows the first and last address in an IPv6 documentation prefix. Calculate 2001:db8::/32

Results

How to read results

The canonical network is the normalized CIDR block after host bits are cleared. First and last address describe the full range covered by the prefix. For IPv4, netmask, broadcast, and usable host counts are included for older network tooling and firewall documentation.

For IPv6, broadcast and dotted-decimal netmask values are marked as not used because IPv6 networks use prefix lengths instead.

Boundaries

Limits

This calculator accepts one IPv4 or IPv6 CIDR network at a time. It does not check whether a public block is assigned to a specific organization; use the IP lookup and ASN guide for that network context.

Next steps

CIDR notation explained A quick explanation of prefix lengths, host bits, and canonical networks. CIDR prefix cheat sheet Scan common IPv4 and IPv6 slash prefixes and address counts. IP in CIDR Check whether one address belongs inside a network range. Range to CIDR Convert raw IP address ranges into CIDR blocks.