Worked example
At 0.745 g/mL, 550 cc/min is about 54.2 lb/hr. A different fuel density changes the result even though the injector's volumetric flow figure is unchanged.
Why density is editable
Petrol blends, ethanol content, temperature and other fuels have different densities. A single hard-coded “10.5 cc/min per lb/hr” rule is convenient but hides that assumption.
Flow rating conditions still matter
Injector ratings also depend on pressure differential and test conditions. This tool converts the stated flow units; it does not correct a flow rating for a different fuel pressure.