IP Subnet Calculator
Enter any IPv4 address and prefix length to instantly calculate network address, broadcast, usable host range, and binary breakdown.
Results
Binary Breakdown
0 Network bits 0 Host bits| Label | Binary | Decimal |
|---|
Common CIDR Reference
Click any row to load that subnet into the calculator.
| CIDR | Subnet Mask | Total IPs | Usable Hosts | Common Use |
|---|---|---|---|---|
/8 | 255.0.0.0 | 16,777,216 | 16,777,214 | Class A private |
/12 | 255.240.0.0 | 1,048,576 | 1,048,574 | Class B private range |
/16 | 255.255.0.0 | 65,536 | 65,534 | Large campus network |
/20 | 255.255.240.0 | 4,096 | 4,094 | Medium office network |
/22 | 255.255.252.0 | 1,024 | 1,022 | Large LAN |
/23 | 255.255.254.0 | 512 | 510 | Medium LAN |
/24 | 255.255.255.0 | 256 | 254 | Standard LAN |
/25 | 255.255.255.128 | 128 | 126 | Half subnet |
/26 | 255.255.255.192 | 64 | 62 | Quarter subnet |
/27 | 255.255.255.224 | 32 | 30 | Small department |
/28 | 255.255.255.240 | 16 | 14 | Small office / VLAN |
/29 | 255.255.255.248 | 8 | 6 | Small server cluster |
/30 | 255.255.255.252 | 4 | 2 | Point-to-point link |
/32 | 255.255.255.255 | 1 | 0 | Host route / loopback |
What Is IP Subnetting?
IP subnetting is the process of dividing a single IP network into smaller, logically segmented sub-networks (subnets). Each subnet operates as its own broadcast domain, which improves network performance, tightens security boundaries, and makes IP address management more efficient.
Network engineers and system administrators use subnetting daily — when designing office LANs, segmenting VLANs in data centres, configuring cloud VPC networks, or planning routed WAN links between sites.
What Is CIDR Notation?
CIDR (Classless Inter-Domain Routing) notation expresses an IP address and its routing prefix together — for example, 192.168.1.0/24. The number after the slash tells you how many bits of the 32-bit address are the network portion; the remaining bits identify individual hosts.
A /24 has 8 host bits, giving 28 = 256 total addresses (254 usable — the network address and broadcast address are reserved). A /30 has just 2 host bits — ideal for point-to-point router links.
Network vs Broadcast Address
Every subnet reserves two addresses: the network address (all host bits set to 0) identifies the subnet itself and cannot be assigned to any device. The broadcast address (all host bits set to 1) is used to send a packet to every host in the subnet simultaneously.
This is why a /24 subnet provides 254 usable host addresses rather than 256 — the first and last are always reserved.
How to Use This Calculator
Enter any IPv4 address in dotted-decimal format (e.g. 10.0.4.0) and set the CIDR prefix using the slider or the prefix field. You can also type a subnet mask directly — the tool keeps all three inputs in sync automatically.
The calculator shows the network address, broadcast address, first and last usable hosts, subnet mask, wildcard mask, total and usable host counts, the IP class, and a full binary breakdown that colour-codes network bits from host bits.