IP Subnet Calculator
Calculate subnet information, network address, broadcast address, host range, convert CIDR/masks, and aggregate subnets with step-by-step solutions.
Calculate
Select a calculation type, enter your values, and click Calculate to see results with step-by-step solution and visualization.
Result
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Step-by-Step Solution
Complete User Guide
What is IP Subnetting?
IP subnetting is the process of dividing a single IP network into smaller sub-networks (subnets). Each subnet has its own network address, broadcast address, and range of usable host addresses. Subnetting helps optimize network performance, improve security, and manage IP address allocation efficiently. The subnet mask defines which portion of an IP address identifies the network and which identifies the host.
5 Calculation Types
Subnet Information
Full details from IP + mask: network, broadcast, host range, class.
Subnet from Hosts
Find the smallest subnet that can hold N hosts.
Subnet from Subnets
Divide a network into N equal subnets.
Supernet (Aggregate)
Combine multiple contiguous subnets into a single summary route.
Convert Mask
Convert between CIDR notation and dotted-decimal masks.
Key Formulas
Network: IP AND Mask
Broadcast: Network OR (NOT Mask)
Total Hosts: 2^(32 − CIDR)
Usable: Total − 2
CIDR from hosts: 32 − ⌈log₂(hosts + 2)⌉
New CIDR: old + ⌈log₂(subnets)⌉
Common CIDR Reference
| CIDR | Mask | Hosts | Usable |
|---|---|---|---|
| /8 | 255.0.0.0 | 16,777,216 | 16,777,214 |
| /16 | 255.255.0.0 | 65,536 | 65,534 |
| /24 | 255.255.255.0 | 256 | 254 |
| /25 | 255.255.255.128 | 128 | 126 |
| /26 | 255.255.255.192 | 64 | 62 |
| /27 | 255.255.255.224 | 32 | 30 |
| /28 | 255.255.255.240 | 16 | 14 |
| /29 | 255.255.255.248 | 8 | 6 |
| /30 | 255.255.255.252 | 4 | 2 |
Important Notes
- This calculator supports IPv4 only.
- Usable hosts = Total − 2 (network + broadcast addresses are reserved).
- Private IP ranges: 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16.
- Supernetting requires contiguous, aligned networks to aggregate properly.