Calculator
Result
–gtt/min
Always verify the provider's order and the drop factor printed on the tubing. Use an infusion pump for high-alert medications.
Formulas
| Tubing | Formula | Shortcut |
|---|---|---|
| Macrodrip 20 gtt/mL | gtt/min = mL × 20 ÷ minutes | mL ÷ (hours × 3) |
| Microdrip 60 gtt/mL | gtt/min = mL × 60 ÷ minutes | mL ÷ hours (= mL/hr) |
| mL per hour | mL/hr = mL ÷ hours | The rate you program on the pump |
Handy relationship: 1 macrodrop (20 gtt/mL) equals 3 microdrops. So when converting from microdrip to macrodrip, divide by 3.
Worked examples
- 1,000 mL over 8 hours with macrodrip tubing (20 gtt/mL): 1000 ÷ (8 × 3) = 41.7 → 42 gtt/min. On a pump: 1000 ÷ 8 = 125 mL/hr.
- 500 mL over 6 hours with microdrip tubing (60 gtt/mL): 500 ÷ 6 = 83.3 → 83 gtt/min (83 mL/hr).
- 100 mL over 30 minutes with macrodrip tubing (20 gtt/mL): 100 × 20 ÷ 30 = 66.7 → 67 gtt/min.
Common mistakes
- Using a drop factor of 20 with tubing that delivers 10 or 15 gtt/mL.
- Dividing by hours when the formula calls for minutes.
- Not recounting the drops after repositioning the patient or changing the bag height.
- Running medications by gravity when they require an infusion pump.
Frequently asked questions
What is the IV drip rate formula for macrodrip tubing?
gtt/min = volume (mL) × drop factor (gtt/mL) ÷ time (min). With 20 gtt/mL tubing, a shortcut is gtt/min = mL ÷ (hours × 3).
How do you calculate drip rate with microdrip tubing?
gtt/min = mL ÷ hours. Because microdrip tubing delivers 60 gtt/mL, the drops per minute equal the mL per hour.
How many drops are in 1 mL?
It depends on the tubing: standard macrodrip sets deliver 10, 15 or 20 gtt/mL and microdrip sets deliver 60 gtt/mL. The drop factor is printed on the tubing package.
Do you round the drip rate?
Yes. Round to the nearest whole drop per minute, since you cannot count part of a drop, and keep monitoring the infusion: gravity flow changes with patient position and bag height.
Standard IV infusion calculation formulas. Text and examples written by our editorial team. Reviewed November 2, 2026. More scales and calculators.