Free Tool
IV Drip Rate Calculator (gtt/min)
Calculate drops per minute for manual gravity infusions.
Formula
gtt/min = (volume in mL × drop factor) ÷ time in minutes
Convert hours to minutes (1 hr = 60 min)
Printed on the tubing packaging. Macrodrip: 10, 15, 20. Microdrip: 60.
Result
Enter values above to calculate.
Worked example
Scenario: Order: 1,000 mL Normal Saline IV over 8 hours. Tubing drop factor: 15 gtt/mL.
- 1Convert time to minutes: 8 hours × 60 min/hr = 480 min.
- 2Apply formula: (1000 × 15) ÷ 480 = 15,000 ÷ 480 = 31.25.
- 3Round to the nearest whole drop: 31 gtt/min.
Set the drip to 31 gtt/min.
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When to use this calculation
Use this calculation any time you set up a gravity-fed IV infusion that isn't controlled by a pump. The drop factor is printed on the tubing package and varies by manufacturer — never assume it. Macrodrip tubing (10, 15, or 20 gtt/mL) is used for most adult fluid infusions; microdrip tubing (60 gtt/mL) is used for slow rates, pediatric patients, or precision-required medications.
Round drips to the nearest whole drop — you can't deliver a fraction of a drop. The most common student error is forgetting to convert hours to minutes before plugging into the formula, which produces an answer 60× too low. If your calculated rate looks wildly off (under 5 gtt/min or over 200), re-check the time conversion first.