PLAY î ONLY. Share this set. For example, if you must administer 1 L (1,000 mL) of fluid over 4 hours, use the first formula to calculate the flow rate, like so: flow rate (mL/hr) = total volume (mL) Ã· infusion time (hr) flow rate (mL/hr) = 1,000 Ã· 4 flow rate (mL/hr) = 250 The flow rate is 250 mL/hr. Study all 3 terms Study 0 îtermterms only.