IP Subnet / CIDR Calculator
Enter an IPv4 address with a prefix (192.168.1.0/24)
or a subnet mask (192.168.1.0 255.255.255.0) and get
the exact network address, broadcast address, usable host range,
and host count — with the /31 and /32
special cases handled correctly, which a plain "total minus 2"
formula gets wrong.
Why does the calculator show a different network address than the IP I entered?
If you enter an address with host bits set, like
192.168.1.137/24, the network address is computed
by zeroing out every bit outside the prefix
(192.168.1.0), not by using your address as-is.
This tool always shows both the address you entered and the
actual network address for the prefix, since confusing the two
is one of the most common subnetting mistakes.
Why do /31 and /32 networks have no separate network or broadcast address?
A /32 identifies exactly one address, so there's
no room for a separate network or broadcast address — it's
just that one host. A /31 has exactly two
addresses, and RFC 3021 defines both as usable host addresses
for point-to-point links, with no broadcast address — a
special case that general-purpose subnetting formulas (total
minus 2) get wrong if not handled explicitly.
Does this tool send my IP ranges anywhere?
No. All parsing and calculation happens entirely in your browser with plain JavaScript. Nothing you enter is uploaded or transmitted.