🎓 Interactive Learning Tool

VPC Subnet Calculator

Master AWS networking by building it — define subnets, pick your VPC size, assign to AZs, and get real CIDRs instantly.

📐 CIDR auto-sizing 🗺️ AZ assignment 📊 Visual diagrams 🔍 IP explorer

Educational use only · Not affiliated with Amazon Web Services

1
Define Subnets
2
VPC Config
3
Assign AZs
4
Calculate
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Subnet Size Reference: How many IPs do I need?

Not sure what prefix to use? Enter your required usable IPs below and we'll show the smallest valid AWS subnet that fits. Use this as a guide when filling in Step 1.

15 50 100 250
AWS always reserves 5 IPs per subnet (network, router, DNS, future use, broadcast).
Smallest
—
Details
Total IPs: —
Usable:    —
/16 /17 /18 /19 /20 /21 /22 /23 /24 /25 /26 /27 /28
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Quiz Mode

Toggle quiz mode on before calculating — results will be hidden and you'll guess the CIDR prefix for each AZ yourself. A great way to test your understanding of IP math.

Toggle on before calculating to challenge yourself.
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What are you building?

1

Define Subnets

Name Type Usable IPs needed
2

VPC Configuration

/
10.0.0.0 10.1.0.0 172.16.0.0 192.168.0.0
3

Assign Subnets to Availability Zones

Results
VPC address space usage
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Architecture Diagram