Cloud Infrastructure
VPC Subnet Planner
Enter a VPC CIDR block and subnet count to compute subnet CIDRs, usable IP counts, and remaining address space. Covers AWS, GCP, Azure, and DigitalOcean VPC models.
Calculations run locally in your browserTool
Example — Representative default scenario — vpc cidr /16 · az count 3 · subnet types public,private,db.
VPC total addresses
65,536
/16 block
Subnet prefix
/19
for 6 subnets
Hosts per subnet
8,190
usable (excl. network+broadcast)
Bits for subnets
3
ceil(log2(6))
About this tool
VPC Subnet Planner
The VPC Subnet Planner divides a CIDR block into subnets by count or size, accounting for provider-reserved addresses, with remaining space calculation.
• Divide a /16 into 6 subnets for a 3-AZ public/private architecture
• Calculate usable IPs per subnet accounting for provider-reserved addresses
• Plan a new VPC without running out of IP space for future subnets
• Compare subnet sizes for a Kubernetes node pool with large pod CIDR requirements
Next step
Continue with Utility Matrix tools for the next decision in this workflow.
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FAQ
What does this tool tell you?
The VPC Subnet Planner divides a CIDR block into subnets by count or size, accounting for provider-reserved addresses, with remaining space calculation.
What affects the result most?
Divides a CIDR block into subnets by count or subnet size — no manual binary math. AWS VPC subnet planning: public, private, and database tiers across 3 AZs. Reserved addresses per subnet: AWS reserves first 4 and last 1 — 5 per subnet minimum.
How should I use the result?
The calculation is deterministic — the same inputs always produce the same output — so the most useful workflow is to vary one input at a time and see which factor moves the result most. That tells you where to focus your attention before committing to a decision.
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