Tools / Subnet Calculator
Subnet / CIDR Calculator
Enter an IPv4 address with a CIDR prefix or netmask to get network range, host count, and broadcast address — all computed in your browser.
// About this tool
Subnet / CIDR Calculator
Enter an IPv4 address with a CIDR prefix (10.0.0.0/24) or a netmask (10.0.0.0 255.255.255.0) and get the full picture of that network: network and broadcast addresses, the usable host range, wildcard mask, IP address class, and whether the range is RFC 1918 private space.
The splitter takes the same network and divides it into equal-sized subnets at a longer prefix — useful for planning VLANs, carving up a /24 into /26s for separate segments, or checking how many /30 point-to-point links fit inside a larger block.
All math runs in your browser with plain integer arithmetic on the address — nothing is looked up or sent anywhere.
// When to use it
Plan a VLAN layout
Enter your allocated block and split it into the subnet size each VLAN needs, then read off each segment's usable range.
Check if two hosts are on the same subnet
Compute the network address for each host's IP/mask — if they match, the hosts share a broadcast domain.
Size a subnet for a host count
Usable hosts = 2^(32 − prefix) − 2. Work backwards from a required host count to the smallest prefix that fits.
// Questions
Does this support IPv6?
No — this calculator is IPv4-only. IPv6 prefix math (/64 subnets, EUI-64) is a large enough topic to warrant its own tool.
Why are usable hosts 2 less than total addresses?
The first address in a subnet is reserved as the network address and the last as the broadcast address, so neither is assignable to a host — except for /31 and /32, which have special-case (0 and non-network) host counts under RFC 3021.
Is my IP address sent anywhere?
No. All calculation happens client-side with integer bit math — nothing is uploaded or logged.
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