IV drip rate calculator
Enter the volume to infuse, the infusion time, and the tubing's drop factor to get the flow rate in mL/hr and the drip rate in drops per minute.
Tubing drop factor
Fill in every field to see the result.
For studying and practice only. This isn't a clinical tool: always follow the prescriber's order, your pharmacist, and your facility's policies.
How IV rates are calculated
mL/hr = volume ÷ hours → gtt/min = mL/hr × drop factor ÷ 60
Worked example
1,000 mL over 8 hours with 15 gtt/mL tubing
- 1000 mL ÷ 8 hr = 125 mL/hr
- 125 × 15 ÷ 60 = 31.25 → 31 gtt/min
Worked example
250 mL over 2 hours with 60 gtt/mL (microdrip) tubing
- 250 mL ÷ 2 hr = 125 mL/hr
- 125 × 60 ÷ 60 = 125 gtt/min
Practice these calculations the way the PTCB exam asks them
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Practice calculation questions freeFrequently asked questions
- What is the formula for IV drip rate?
- Drip rate (gtt/min) = volume (mL) × drop factor (gtt/mL) ÷ time (minutes). Equivalently, find mL/hr first, then multiply by the drop factor and divide by 60.
- What is a drop factor?
- The number of drops that make 1 mL with a given IV tubing set, printed on the tubing package. Macrodrip sets are usually 10, 15 or 20 gtt/mL; microdrip sets are 60 gtt/mL.
- Why is gtt/min the same as mL/hr with microdrip tubing?
- With 60 gtt/mL tubing, multiplying by 60 drops per mL and dividing by 60 minutes cancel out, so the drip rate in gtt/min equals the flow rate in mL/hr.
- Do you round the drip rate?
- Yes, to a whole drop, because you can't count a fraction of a drop. Infusion pumps are set in mL/hr instead, which can include decimals.