What is a subnet calculator?

A subnet calculator is a tool that computes network parameters from an IP address and CIDR prefix. It derives the network address, broadcast address, usable IP range, subnet mask, and wildcard mask using bitwise operations.

How do I calculate usable hosts?

Usable hosts = 2^(32-CIDR) - 2. The -2 accounts for the network and broadcast addresses which cannot be assigned to devices. For example, a /24 network has 2^8 - 2 = 254 usable hosts.

What is the difference between network and broadcast address?

The network address is the first address in a subnet (all host bits set to 0) and identifies the subnet itself. The broadcast address is the last address (all host bits set to 1) and is used to send data to all devices on the subnet.

What is a wildcard mask?

A wildcard mask is the bitwise inverse of a subnet mask. It is used in Cisco ACLs and OSPF routing to match IP address ranges. For example, the wildcard mask for 255.255.255.0 is 0.0.0.255.

What CIDR should I use for my network?

/24 (255.255.255.0) is the most common choice for small networks with up to 254 devices. Use /16 for larger networks (65,534 hosts), /30 for point-to-point links (2 hosts), and /32 for loopback addresses.

Is this subnet calculator accurate?

Yes. All calculations use pure JavaScript bitwise operations with no server round-trip. The tool has been tested against standard networking references and produces identical results to Cisco IOS and other professional networking tools.

IP Subnet Calculator

Enter an IP address and CIDR prefix to calculate all subnet parameters. Our free subnet calculator uses pure bitwise AND operations to derive the network address, then applies the wildcard mask to compute the broadcast address and usable host range. Results include network address, broadcast, subnet mask, wildcard mask, first and last usable IP, usable hosts, and total hosts — all computed instantly in your browser with no server round-trip.

IP Address

Accepts IP/CIDR, IP Mask, or IP/MASK formats

How Subnet Calculation Works

AND the IP with the subnet mask → network address. OR the network with the wildcard → broadcast address. Usable hosts = 2^(32-CIDR) - 2.

Learn more about subnet masks →