Subnet Calculator
Work out network boundaries, host ranges and masks for any IPv4 or IPv6 block — instantly, and entirely in your browser.
Network or address
Accepts 10.0.0.0/8, 10.0.0.1 255.0.0.0 or a bare address. Everything is calculated in your browser.
Network 192.168.1.128/26
Private (RFC 1918)Details
Reading CIDR notation
The number after the slash is how many bits are fixed as the network portion. In 192.168.1.0/24 the first 24 bits identify the network, leaving 8 bits — 256 addresses — for hosts.
Two of those are normally unavailable: the first identifies the network itself, and the last is the broadcast address. That is why a /24 gives you 254 usable hosts rather than 256.
The special cases
/31 networks
On point-to-point links, RFC 3021 allows a /31 to use both addresses as hosts — there is no broadcast to reserve. This calculator accounts for that.
/32 networks
A /32 is a single address, commonly used for loopback interfaces and for pinning a route to exactly one host.