How to use
- Enter data or choose generation settings.
- Run the tool and review the values and any messages.
- Copy the result or download a local file.
IP Subnet Calculator
Calculate IPv4 and IPv6 CIDR ranges, subnet masks and exact address counts.
Processing runs in your browser. Your input is not sent to DevToolsy.
How it works
Enter an IP and prefix or a complete CIDR. For IPv4, a contiguous dotted mask is accepted. Optional checks test address membership and split the range into up to 256 child subnets.
192.0.2.123/24{
"family": "ipv4",
"cidr": "192.0.2.0/24",
"address": "192.0.2.123",
"prefix": 24,
"netmask": "255.255.255.0",
"network": "192.0.2.0",
"firstAddress": "192.0.2.0",
"lastAddress": "192.0.2.255",
"addressCount": "256",
"hostBits": 8,
"hostOffset": "123",
"wildcard": "0.0.0.255",
"broadcast": "192.0.2.255",
"firstHost": "192.0.2.1",
"lastHost": "192.0.2.254",
"usableHosts": "254"
}Calculate IPv4 and IPv6 CIDR ranges, subnet masks and exact address counts.
Options and data fidelity
IPv6 has no broadcast address. Address counts describe the range, not how many endpoints can be assigned. IPv4 /31 uses point-to-point endpoints; /32 is one host route. List up to 256 child subnets; address ranges are calculated without enumerating hosts.
Working with the result
This is local address arithmetic. It does not ping hosts, query DNS or verify that a network can be assigned or routed.
Yes. Results have copy and download actions. Changing inputs or generation settings invalidates the previous result.
Text input up to 1 MiB; User-Agent up to 16 KiB. Shorter limits apply to address and identifier fields. Up to 1,000 ULIDs, 10,000 placeholder words or 256 child subnets. Tasks time out after 10 seconds.
Frequently asked questions
Which address and mask inputs work?
Enter an IP and prefix or a complete CIDR. For IPv4, a contiguous dotted mask is accepted. Optional checks test address membership and split the range into up to 256 child subnets.
How are hosts and IPv6 counts handled?
IPv6 has no broadcast address. Address counts describe the range, not how many endpoints can be assigned. IPv4 /31 uses point-to-point endpoints; /32 is one host route. List up to 256 child subnets; address ranges are calculated without enumerating hosts.
Does this test whether a host is reachable?
This is local address arithmetic. It does not ping hosts, query DNS or verify that a network can be assigned or routed.
Is my input uploaded?
Processing runs in your browser. Your input is not sent to DevToolsy.
Can I copy or download the result?
Yes. Results have copy and download actions. Changing inputs or generation settings invalidates the previous result.