Free network calculator
IPv4 Subnet & CIDR Calculator
An IPv4 CIDR block combines an address with a prefix length from /0 to /32. The prefix identifies network bits; the remaining bits identify addresses inside the block. This calculator normalizes any IPv4/CIDR input and returns its network, broadcast, mask, wildcard, total addresses, usable range, and input-address classification.
Last updated: July 19, 2026 · No sign-up · Runs in your browser
Examples: ·
Normalized network
—
Network address
—
Broadcast address
—
Subnet mask
—
Wildcard mask
—
Usable range
—
Total / usable addresses
—
—
How IPv4 CIDR calculation works
The calculator converts IPv4 octets to one unsigned 32-bit integer, builds the prefix mask, applies a bitwise AND for the network, fills host bits for the broadcast address, and converts the values back to dotted decimal. Traditional subnets reserve network and broadcast addresses; /31 point-to-point links follow RFC 3021, and /32 represents one address.
| Prefix | Subnet mask | Total addresses | Usable in this calculator |
|---|---|---|---|
| /8 | 255.0.0.0 | 16,777,216 | 16,777,214 |
| /16 | 255.255.0.0 | 65,536 | 65,534 |
| /24 | 255.255.255.0 | 256 | 254 |
| /30 | 255.255.255.252 | 4 | 2 |
| /31 | 255.255.255.254 | 2 | 2 for point-to-point use |
| /32 | 255.255.255.255 | 1 | 1 host address |
Primary references
- RFC 4632: Classless Inter-domain Routing (CIDR) — IPv4 CIDR addressing and aggregation strategy.
- RFC 3021: Using 31-Bit Prefixes on IPv4 Point-to-Point Links — use of both addresses in a /31 for point-to-point links.
Frequently asked questions
What does /24 mean in IPv4 CIDR notation?
A /24 prefix uses 24 bits for the network and leaves 8 address bits. That creates 256 total addresses; a traditional subnet has 254 usable host addresses after reserving network and broadcast addresses.
How many usable addresses are in a /31?
RFC 3021 allows both addresses in a /31 on an IPv4 point-to-point link, so the calculator reports two usable endpoint addresses. Do not assume /31 support for a general LAN or every provider.
Is a /32 a subnet?
A /32 identifies one IPv4 address and is commonly used as a host route. It has no separate address range beyond that single address.
What is a wildcard mask?
A wildcard mask is the bitwise inverse of the subnet mask. Network devices and access-control syntax may use it, but exact behavior depends on the platform.
Continue exploring
Related free tools
Move from this result to a related planning, infrastructure, or validation task. Each tool is free to use without sign-up.