A walkthrough, end to end.
- 1
Enter an IPv4 address with prefix length (e.g. 192.168.1.10/24).
- 2
See the network, broadcast, mask, wildcard, and usable host range.
- 3
Total host count and class are also shown.
CIDR math
/n means n leading 1 bits in the mask. Network = IP AND mask. Broadcast = network OR ~mask. Usable hosts = 2^(32−n) − 2 (except /31 and /32).
What you can do with this.
Home / office network design
Plan a /24 LAN with up to 254 hosts.
Cloud VPC sizing
Pick a /16 or /20 for your VPC.
VLAN planning
Carve out /27 or /28 sub-blocks.
Firewall rules
Translate /24 into mask 255.255.255.0.
Subnetting practice
Verify CCNA-style subnet questions.
DHCP scope
Find the usable host range to configure DHCP.
Routing tables
Convert between CIDR and dotted mask.
IPv4 subnetting 2026 — what's current
Standard since RFC 4632 (2006).
Frequently asked.
This calculator handles IPv4 only.
/31 has 2 hosts (RFC 3021 point-to-point); /32 has 1 (host route).
No. All math runs in your browser.
Classful designations are largely historic but the calculator labels the address class for reference.