IP Subnet Calculator
Enter an IPv4 address and CIDR prefix to calculate all subnet details
IPv4 Address
CIDR Prefix Length
/
0 (no mask) to 32 (single host)
Common Subnets
/8 → 16,777,214 hosts
/16 → 65,534 hosts
/24 → 254 hosts
/30 → 2 hosts (point-to-point)
/32 → 1 host (single IP)
Subnet Details
CIDR Notation
—
Network Address
—
Broadcast Address
—
Subnet Mask
—
Wildcard Mask
—
First Usable Host
—
Last Usable Host
—
Total Usable Hosts
—
IP Class
—
Private IP?
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IP Subnetting Explained
A subnet divides a large IP network into smaller segments. The CIDR (Classless Inter-Domain Routing) prefix /n tells you how many bits are fixed for the network portion. The remaining bits identify individual hosts. A /24 network has 2⁸ = 256 addresses, minus 2 (network + broadcast) = 254 usable hosts.
The wildcard mask (inverse of subnet mask) is used in Cisco ACLs and OSPF routing configurations. Private IP ranges (RFC 1918) — 10.x.x.x, 172.16–31.x.x, 192.168.x.x — are not routable on the public internet and are used for internal networks.
lightbulb Example
192.168.1.50 /24:
1Network: 192.168.1.0
2Mask: 255.255.255.0
3Hosts: .1 → .254
✓ 254 usable hosts, Private IP