How the iv drip rate calculator works
Infusions are run either on a pump, which is set in millilitres per hour, or by gravity, where the nurse counts drops in the drip chamber. The drop factor is how many drops make one millilitre with that tubing.
Drip rate (gtt/min) = Volume (mL) × Drop factor (gtt/mL) ÷ Time (min)
Macrodrip sets deliver 10, 15 or 20 drops per mL and are used for routine adult fluids. Microdrip sets deliver 60 drops per mL, used for small, precise volumes such as in paediatrics. A handy shortcut: with a 60 gtt/mL set, drops per minute equal mL per hour.
Worked example
An order calls for 1,000 mL of normal saline over 8 hours with 15 gtt/mL tubing. The pump rate is 1,000 ÷ 8 = 125 mL/hr. By gravity, 1,000 × 15 ÷ 480 minutes = 31.25, so you would regulate to 31 gtt/min, about one drop every 2 seconds.
For education only. Not medical advice; confirm with a qualified clinician.
Frequently asked questions
What is a drop factor?
The number of drops that equal 1 mL for a given IV tubing set, printed on its package.
How do I calculate mL per hour?
Divide the total volume in mL by the infusion time in hours.
When are microdrip sets used?
For slow or precise infusions, such as paediatric or medication drips, typically under 100 mL/hr.
Should I round drops per minute?
Yes, to the nearest whole number, because partial drops cannot be counted.
Updated October 2026. Results are estimates for education, not financial or medical advice. All math runs in your browser; nothing you type is sent anywhere.