IV drip rate for 1000 mL over 8 hours, solved step by step

Problem. A nurse must give 1000 mL of saline over 8 hours using a gravity IV set with a drop factor of 15 gtt/mL (drops per millilitre). How many drops per minute should the drip run at, and what is the equivalent pump rate in mL/h?

Step by step

1. Write the formula: drops per minute = (volume in mL × drop factor in gtt/mL) ÷ time in minutes.

2. Convert the time to minutes: 8 hours × 60 minutes per hour = 480 minutes.

3. Multiply the volume by the drop factor: 1000 mL × 15 gtt/mL = 15,000 drops in total.

4. Divide the total drops by the total minutes: 15,000 ÷ 480 = 31.25 gtt/min.

5. Round to a rate that can actually be counted: 31.25 ≈ 31 gtt/min.

6. For a pump, skip the drop factor: 1000 mL ÷ 8 h = 125 mL/h.

7. Check the result: 125 mL/h ÷ 60 = about 2.08 mL/min, and 2.08 × 15 ≈ 31.25 gtt/min, which matches.

Answer: The drip should run at (1000 × 15) ÷ 480 = 31.25 ≈ 31 gtt/min, which is 125 mL/h on a pump.

This assumes a 15 gtt/mL set and a constant rate, and rounding to 31 gtt/min makes the infusion run very slightly slower than ordered, so real practice follows local protocols and the prescriber's order.