Enter an IP and a mask (CIDR or dotted-decimal) to get the network address, broadcast address, usable host range and host count.
IP addressSubnet mask
Tip: the mask can be CIDR like /24 or dotted-decimal like 255.255.255.0.
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AD · LEADERBOARD 728×90 (PLACEHOLDER — REPLACED WHEN ADSENSE GOES LIVE)
FAQ
What is CIDR?
CIDR (Classless Inter-Domain Routing) expresses the mask length as a "/number", e.g. /24 means the first 24 bits are network and the last 8 are host bits — equivalent to the dotted-decimal mask 255.255.255.0.
Why subtract 2 from the host count?
The network address (all host bits 0) and the broadcast address (all host bits 1) cannot be assigned to hosts, so usable hosts = 2^(host bits) − 2. The /31 (point-to-point) and /32 (single IP) cases are exceptions and do not subtract 2.
Is my IP uploaded?
No. All computation happens locally in your browser; the IP and mask you enter are never sent to any server.