SUBNET
CALCULATOR
Enter an IPv4 address with a CIDR prefix, like 192.168.1.0/24, to break the block down instantly: the network and broadcast addresses, the first and last usable host, the total and usable host count, the subnet mask and its wildcard, and whether the range is public or private. Everything is calculated in your browser.
Calculated in your browser. Planning a network or a dedicated IP block? Compare hosts with the infrastructure to match.
Find a host with AI MatchWhat is a Subnet Calculator?
A subnet calculator is a free tool that takes an IPv4 address in CIDR notation and works out the network and broadcast addresses, the usable host range, the total and usable host count, and the subnet mask with its wildcard. It reveals how an IP block is divided, which is essential for planning networks and configuring routers and firewalls.
How does a Subnet Calculator work?
- 01Enter an IPv4 address and prefix in CIDR notation (address/bits).
- 02We apply the mask to derive the network, broadcast and host range.
- 03The netmask, wildcard, host counts and address class are computed locally.
Frequently asked questions
What does the /24 in an IP address mean?
The number after the slash is the CIDR prefix: how many bits of the address identify the network rather than the host. A /24 fixes the first 24 bits, leaving 8 bits for hosts, which is 256 addresses (254 usable). A smaller number means a bigger network: /16 is 65,536 addresses, /8 is over 16 million. Each step down doubles the size.
Why are there two fewer usable hosts than total addresses?
In a normal subnet the first address is the network identifier and the last is the broadcast address, so neither can be assigned to a device. A /24 has 256 total but 254 usable. The exceptions are /31, which RFC 3021 defines as 2 usable addresses for point-to-point links, and /32, a single host route.
What is the difference between the netmask and the wildcard mask?
The netmask marks the network bits as 1s (255.255.255.0 for a /24); the wildcard is its inverse, marking the host bits as 1s (0.0.0.255). Netmasks are used in interface and routing configuration, while wildcard masks are what Cisco ACLs and OSPF expect. This tool shows both so you do not have to invert one by hand.