System Design Calculator
Back-of-envelope calculations for system design interviews. Estimate QPS, storage, and bandwidth requirements.
Example Presets
Practice with typical system design scenarios. Values are approximate for learning.
Input Parameters
Enter your system requirements
100.00 M users
Text ~1KB, Image ~500KB, Video ~50MB
Typical: 2-3x for normal apps, 10x for viral events
Queries Per Second (QPS)
11.57 K
Average QPS
23.15 K
Peak QPS (2x)
Request Volume
1.00 B
Daily Requests
30.00 B
Monthly Requests
Storage Requirements
1.00 TB
Per Day
30.00 TB
Per Month
365.00 TB
Per Year
1.82 PB
5 Year Total
Bandwidth
92.59 Mbps
Avg Bandwidth
185.19 Mbps
Peak Bandwidth
View text version
System Design Estimates ======================== Daily Active Users: 100.00 M Requests per User: 10 Data per Request: 1 KB QPS (avg): 11.57 K QPS (peak 2x): 23.15 K Daily Requests: 1.00 B Monthly Requests: 30.00 B Storage/Day: 1.00 TB Storage/Month: 30.00 TB Storage/Year: 365.00 TB Storage (5 years): 1.82 PB Bandwidth: 92.59 Mbps
Quick Reference Numbers
Memorize these for interviews
1 day
86,400 seconds
1 month
2.5M seconds
1 year
31.5M seconds
1 KB
1,000 bytes
1 MB
1,000 KB
1 GB
1,000 MB
1 TB
1,000 GB
1 PB
1,000 TB
Practice System Design Visually
Use our interactive System Design Canvas to build architectures with drag-and-drop components and get AI feedback on scalability, reliability, and performance.
Back-of-Envelope Tips
Common Approximations:
- • 1 day ≈ 100K seconds (actually 86.4K)
- • 1 month ≈ 2.5M seconds
- • 1 year ≈ 30M seconds
- • Read:Write ratio ≈ 100:1 for most apps
- • Peak traffic ≈ 2-3x average
Typical Data Sizes:
- • Tweet/Message: 1 KB
- • User profile: 10 KB
- • Thumbnail: 50 KB
- • Image: 200 KB - 2 MB
- • 1 min video: 50 MB
More Interview Tools
Put it into practice
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