Estimation Calculator

Back-of-envelope calculations for system design interviews. Adjust the inputs and see results instantly.

Convert daily requests to Queries Per Second

Inputs

Daily Active Usersusers

e.g., 10M

Requests per user per dayrequests

Average actions/day

Peak multiplierx

Peak is typically 2-3x average

Total daily requests100.0M

Average QPS1.2K

Peak QPS3.5K

1M req/day~12 QPS

1B req/day~12K QPS

Seconds/day86,400

1M x 1KB= 1 GB

1B x 1KB= 1 TB

RAM access100 ns

SSD read150 us

HDD seek10 ms

Same DC RTT500 us

Cross-continent150 ms

1 char (ASCII)1 byte

1 char (UTF-8)1-4 bytes