Subnet Calculator
Calculate subnets, CIDR notation, usable hosts, and broadcast addresses. Essential for VLAN design, IP planning, and network segmentation.
Calculate
IP Subnet Calculator
Enter an IPv4 address and CIDR prefix to get complete subnet details.
Use Cases
When You Need a Subnet Calculator
Proper subnetting is the foundation of every secure, scalable network.
VLAN Design
Properly size subnets for each VLAN — data, voice, guest, IoT — to avoid address exhaustion or waste.
Network Segmentation
Design security zones with right-sized subnets. Smaller subnets reduce the blast radius of breaches.
Multi-Site Planning
Plan addressing schemes across branch offices, data centers, and cloud VPCs with non-overlapping ranges.
Quick Reference
Common CIDR Block Sizes
Choose the right prefix length based on how many hosts you need.
| CIDR | Subnet Mask | Usable Hosts | Typical Use |
|---|---|---|---|
| /24 | 255.255.255.0 | 254 | Standard LAN |
| /25 | 255.255.255.128 | 126 | Small department |
| /26 | 255.255.255.192 | 62 | Voice VLAN |
| /27 | 255.255.255.224 | 30 | Server subnet |
| /28 | 255.255.255.240 | 14 | DMZ / management |
| /30 | 255.255.255.252 | 2 | Point-to-point link |
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