IP Subnet Calculator is a free online tool for IPv4/IPv6 CIDR calculation, subnet splitting, and VLSM allocation. Computes network address, broadcast, host range, and subnet mask entirely in your browser.
What is a Subnet Calculator?
A subnet calculator computes network properties from a CIDR notation input. It determines the network address, broadcast address, usable host range, and subnet mask for both IPv4 and IPv6 networks.
Common Use Cases
Network Design
Plan IP address allocation for subnets, determine appropriate CIDR prefixes for given host counts, and verify subnet configurations.
VLSM Planning
Allocate variable-length subnet masks to efficiently use address space when different subnets have different host requirements.
How to Use the Subnet Calculator
- 1
Enter a CIDR address
Type an IP address with CIDR prefix (e.g. 192.168.1.0/24) to see network properties including broadcast, host range, and subnet mask.
- 2
Split or allocate subnets
Switch to the Subnet Splitter tab to divide a network into equal subnets, or use the VLSM Allocator for variable-length allocation.
- 3
Copy results
Click the copy button next to any result field to copy it to your clipboard.