IPv4 Subnet Calculator
Calculate IPv4 network, broadcast, usable host range, netmask, and wildcard from CIDR notation. /31 follows RFC 3021 with two usable addresses; /32 represents one host.
About IPv4 Subnet Calculator
IP Subnet Calculator does the CIDR math sysadmins do daily: give it 10.0.0.0/16 or 192.168.1.37/24 and it returns the network and broadcast addresses, usable host range and count, netmask and wildcard mask. Handles the /31 and /32 edge cases correctly. Pure local math — your network layout isn't something to type into a random website.
- Category
- dev
- Input
- No file input — params only.
- Output
- Outputs: application/json.
- Cost
- Free, runs in your browser
- Memory
- low
Common uses
- Work out the usable host range before carving up a VPC
- Check whether two addresses land in the same subnet
- Translate between prefix length and dotted netmask for a firewall rule
- Verify a /31 point-to-point link really has two usable addresses
- Sanity-check a subnet plan before writing it into infrastructure code
Frequently asked questions
What do I enter?
An IPv4 CIDR — a network like 10.0.0.0/16, or any address with a prefix like 192.168.1.37/24 (the tool reports which network that address belongs to).
What comes back?
Network address, broadcast, first and last usable hosts, usable host count, netmask and wildcard mask in dotted form, and whether your input was the network address itself.
Does it handle /31 and /32?
Yes, per RFC 3021: a /31 has exactly two usable addresses (point-to-point), and a /32 is a single host with no broadcast semantics.
IPv6?
Not yet — this version is IPv4. IPv6 support is a natural follow-up; tell us if you need it.
Is anything sent to a server?
No. It's pure arithmetic in your browser.
Keywords
- ipv4
- cidr
- subnet
- network
- broadcast
- netmask
- wildcard
- rfc 3021
- calculator