CIDR Calculator
betaThis free CIDR calculator takes an IPv4 address and prefix (e.g. 192.168.1.0/24) and works out the network and broadcast addresses, subnet and wildcard masks, first and last usable host, host count and address class — instantly, entirely in your browser.
Enter an IPv4 or IPv6 address with a CIDR prefix (e.g. 192.168.1.0/24 or 2001:db8::/32) to see the network, range, mask and address count. Everything is computed in your browser.
How to use CIDR Calculator
- 1 Enter an IPv4 address with a CIDR prefix, e.g. 10.0.0.0/24.
- 2 Read the network, broadcast, netmask and wildcard mask.
- 3 Check the first/last usable host and the host count.
- 4 Copy the full breakdown with one click.
Frequently asked questions
What does /24 mean?
The number after the slash is the CIDR prefix — how many leading bits are the network portion. /24 means the first 24 bits are the network, leaving 8 bits (256 addresses, 254 usable hosts).
How are /31 and /32 handled?
A /32 is a single host. A /31 is a two-address point-to-point link (RFC 3021), so both addresses are usable — the calculator accounts for both.
Is my input uploaded?
No. All calculations run locally in your browser; nothing is sent anywhere.
Does it support IPv6?
This calculator focuses on IPv4 subnetting. IPv6 support may come later.