IV Drip Rate Calculator (mL/hr and Drops per Minute)
Enter the volume, infusion time and the tubing drop factor to get the flow rate in mL/hour and gtt/min.
✓ Formulas cited from the published literature
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About this calculator
Gravity IV sets deliver a fixed number of drops per millilitre, called the drop factor. To run an infusion over the right time, you convert the ordered volume and duration into a rate in drops per minute, or set an infusion pump in mL/hour.
How it works
Flow rate (mL/hr) = volume (mL) ÷ time (hr)
Drip rate (gtt/min) = volume (mL) × drop factor (gtt/mL) ÷ time (min)
Macro sets are usually 10, 15 or 20 gtt/mL; micro (paediatric) sets are 60 gtt/mL, which makes gtt/min equal to mL/hr.
How to read your result
The drop factor is printed on the IV set packaging. Round the drip rate to the nearest whole drop and recount over a full minute after adjusting the roller clamp.
Worked example
1,000 mL over 8 hours using a 15 gtt/mL set.
| Flow rate | 125 mL/hour |
| Drip rate | 31 drops/min About 1 drop every 1.9 seconds |
Frequently asked questions
What is a drop factor?
The number of drops that make 1 mL for a particular tubing set. It is printed on the packaging.
How do I calculate gtt/min?
Volume × drop factor ÷ time in minutes. For 1,000 mL over 8 hours with a 15 gtt/mL set: 1000 × 15 ÷ 480 ≈ 31 gtt/min.
Can I use this for paediatric infusions?
The maths is the same, but paediatric infusions require pumps and strict protocols. Verify every calculation independently.
Limitations and when not to use
Calculation aid only. Not a substitute for pump programming checks or medication orders. Not for high-alert drugs without independent verification.
Sources and references
- Standard nursing and pharmacy calculation references (volume × drop factor ÷ time).
Last updated: 2026-10-09