CIDR / Subnet Calculator

Calculate network address, broadcast, host ranges, masks, and address counts for any CIDR block. Runs entirely in your browser.

How it works

• The address is converted to a 32-bit integer; the prefix length selects how many leading bits form the network part.
• Network address zeroes the host bits; broadcast sets them all to 1.
• Usable hosts is total addresses minus network and broadcast (unless the block is /31 or /32, which have no broadcast).
• The wildcard mask is the bitwise inverse of the subnet mask.

About CIDR / Subnet Calculator

CIDR (Classless Inter-Domain Routing) describes networks as IP/prefix, where the prefix is the number of leading 1-bits in the subnet mask. /24 means 24 network bits and 8 host bits — 256 addresses. Knowing the network address, broadcast address, and usable host range is the first step in any IP planning task: assigning static addresses, sizing VPC/VNet subnets in AWS, Azure, or GCP, writing firewall rules, or debugging why two services cannot reach each other.

Remember that network and broadcast addresses are reserved in normal subnets, so a /24 has 254 usable hosts, not 256. Point-to-point links often use /31 (2 addresses, no broadcast) or /30 (4 addresses, 2 usable). RFC 1918 private ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) are what most internal networks use — this tool helps you carve them correctly.