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.
No data is transmitted — everything runs locallyTool
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
Affiliate disclosure
Developer-friendly cloud infrastructure. DigitalOcean provides cloud compute, networking, and managed databases with predictable pricing.
View VPCs options on DigitalOcean
External site · Independent provider · We may receive a commission · Not a recommendation
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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