IP/CIDR calculator
Subnet analysis · mask conversion · IP membership · subnet splitting
CIDR 分析
掩码互转
子网划分
IP 归属子网（最长前缀匹配）
FAQ
CIDR to network address / broadcast address / total hosts (usable hosts = total minus 2, with /31 giving 2 and /32 giving 1); subnet-mask conversion (255.255.255.0 to /24 and back); which subnet an IP belongs to (longest prefix match - when several subnets match, the most specific one wins); subnetting (splitting one subnet evenly into a power-of-two number of pieces).
By the classic subnetting convention, the address with all host bits 0 is the network address and all-1 is the broadcast address - neither can be given to a host; /31 is a point-to-point link (RFC 3021) where both addresses are usable; /32 is the host itself.
A form like 192.168.001.1 is ambiguous (decimal or octal?), and quite a few network tools parse it as octal and get bitten. This page rejects it outright - please use plain decimal notation.
No. Everything is 32-bit integer arithmetic done locally in your browser, with no requests at all; reloading clears it.