Developer Tools
Subnet Calculator
CIDR to netmask, range, broadcast and usable hosts — pure local bit-maths.
✓ Free
✓ No account
◉ Runs on this device
Developer Tools
Powering up the tool…
TOOL SUBNET-CALCU
What this tool does
About the subnet calculator
/31 and /32 special cases handled per RFC, nothing probed.
How to use it
- Enter address/prefix (e.g. 10.0.0.0/22).
- Read mask, network, broadcast, range, hosts.
- Note the wildcard mask for ACL syntaxes.
- All computed locally — no network was consulted.
Useful for
- Size a subnet for a VPC or VLAN.
- Check whether an IP belongs to a range.
- Explain the missing-two-hosts question once and for all.
Straight answers
Subnet Calculator FAQ
Why usable hosts = 2ⁿ − 2?
The all-zeros address names the network and all-ones is broadcast — reserved by convention on ordinary subnets. /31 point-to-point links (RFC 3021) and /32 single hosts play by their own rules, which the tool applies.
What is the wildcard mask for?
The bitwise inverse of the netmask — Cisco ACLs and some firewall syntaxes want it. Printed so you never hand-invert octets at 2am.