Visual Subnet Calculator
Interactively split and visualize IP address ranges. Plan subnets with a visual map, hierarchy tree, and detailed table. Export your subnet plan as CSV or text.
Enter a CIDR range to visualize (e.g. 10.0.0.0/16). Click "Split" on any subnet to divide it into two halves.
Subnet Planning Guide
How Visual Subnet Splitting Works
Start with a parent CIDR range (e.g. 10.0.0.0/16) and split it into two
equal halves by increasing the prefix by 1. A /16 becomes two /17s,
each /17 can be split into two /18s, and so on down to /32.
This is the basis of VLSM (Variable Length Subnet Masking) -- allocating
different-sized subnets as needed.
AWS VPC Subnet Planning
A typical AWS VPC uses 10.0.0.0/16 (65,536 IPs). Best practices:
- Split into
/20s or/24s per Availability Zone - Separate public subnets (load balancers) from private (app servers, databases)
- Reserve space for future growth -- don't allocate everything immediately
- AWS reserves 5 IPs per subnet (first 4 + broadcast)
Home and Office Networks
Most home networks use 192.168.1.0/24 (254 usable hosts). For larger setups:
- Use
/22for ~1000 devices across VLANs - Split by purpose: IoT on one subnet, workstations on another
- A
/28(14 hosts) works well for a management VLAN - Point-to-point links between routers use
/30or/31
CIDR Subnet Size Reference
Quick reference for common subnet sizes:
/8-- 16,777,216 IPs (Class A)/16-- 65,536 IPs (Class B / VPC)/20-- 4,096 IPs (large subnet)/24-- 256 IPs (Class C / standard LAN)/28-- 16 IPs (small segment)/30-- 4 IPs (point-to-point)/32-- 1 IP (single host route)