System Design Calculator

System Design Calculator helps engineers make fast back-of-the-envelope estimates for architecture planning and interviews.

Use focused calculators for common system design questions:

- Users and traffic: convert daily active users into average and peak QPS.
- Storage: estimate retention, replication, and index overhead.
- Bandwidth: calculate ingress, egress, and monthly transfer.
- Throughput and concurrency: apply Little's Law to request load.
- Cache sizing: estimate hot working sets for Redis or Memcached.
- RAM per server: size memory for sessions and connection state.
- Media streaming: estimate bandwidth and storage for audio and video services.
- AI inference: estimate GPU memory and throughput requirements.
- WebSocket and real-time systems: estimate fan-out, connection memory, and server count.

The app supports shorthand numeric input such as 10k, 1.5m, and 2B, includes compact and full-size layouts, and keeps calculations local on your Mac.