About the subnet calculator
A subnet calculator works out the details of an IPv4 network from an IP address and a CIDR prefix (or subnet mask). It shows the network and broadcast addresses, the usable host range, the subnet and wildcard masks, the number of total and usable hosts, the IP class, whether the address is public or private, and the network in binary. It is an essential tool for network administrators and anyone studying networking.
How Subnet Calculator works
How to use the subnet calculator
- Enter an IPv4 address (for example 192.168.1.10).
- Choose a CIDR prefix from /0 to /32 — the matching subnet mask is shown beside it.
- All the subnet details update instantly below.
What the results mean
The network address is the first address in the block and the broadcast address is the last; the usable host range is everything in between. The subnet mask defines how many bits are the network portion, and the wildcard mask is its inverse (used in ACLs). Usable hosts equal total addresses minus the network and broadcast addresses.
CIDR in brief
CIDR notation like /24 means the first 24 bits identify the network, leaving 8 bits (256 addresses, 254 usable) for hosts. Smaller prefixes mean bigger networks: /16 has 65,536 addresses, /30 has just 4.
Common uses
- Plan and size IP subnets
- Find the network and broadcast address
- Work out the usable host range
- Convert between CIDR prefix and subnet mask
- Count usable hosts in a subnet
- Check if an IP is public or private
- Study for networking exams (CCNA, etc.)
- Build firewall and ACL rules with wildcard masks