Med-Math Dosage Calculations Practice Test

Calculating IV flow rate uses volume, time, and drop factor. The drop factor tells how many drops make up 1 mL, so you multiply the volume by the drop factor to get the total drops, then divide by the infusion time in minutes.

Here, 500 mL to be infused over 8 hours with a drop factor of 20 gtt/mL. Convert time to minutes: 8 hours × 60 minutes/hour = 480 minutes. Multiply volume by drop factor: 500 mL × 20 gtt/mL = 10,000 drops. Now divide by time: 10,000 drops ÷ 480 minutes ≈ 20.83 drops per minute. Rounding to the nearest whole drop gives 21 gtt/min.

So the flow rate is about 21 drops per minute. The exact calculation yields 20.83, which rounds to 21, matching the chosen result.