Make the decision from your job
A speed setting alone cannot tell you whether extrusion is realistic. Change width, height, or speed and check the resulting flow; validate the limit with your own material and printer rather than copying a number from another setup.
Use a calculator after the concept is clear
Use the linked workbench tools to test your own dimensions, costs, or production assumptions. The calculator provides the arithmetic; this guide explains the decision around it.
Keep a written baseline for a repeatable job: material, nozzle, layer plan, speed, cost inputs, and the result you accepted. Change one variable at a time when you need to diagnose a difference.
Common failure mode
Copying a value from an unrelated printer, material, or part often creates false confidence. Check preview, measure a representative result, and revise the input when the real process disagrees.