Why tank litres do not answer the question
A large receiver can provide a useful buffer, but once stored air is used the pump still has to replenish it. Two compressors with similar tank sizes can have very different delivered airflow.
Calculate realistic simultaneous demand
For one-person home use, many tools may never overlap. A commercial workshop with several technicians can have genuinely simultaneous demand. Size around the way the garage operates.
Understand FAD and displacement
Manufacturers may publish theoretical displacement as well as free-air delivery or another delivered-air figure. For sizing, prefer a clearly stated delivered output at a relevant pressure and compare like with like.
Check power before choosing the machine
Higher-output compressors can require dedicated electrical circuits or three-phase supply. Confirm the manufacturer’s electrical requirements and use a competent electrician where required.
Tool-demand figures and this guidance are planning aids. Confirm the actual airflow and pressure requirements of your tools and the compressor manufacturer’s delivered-air specification before buying or installing equipment.