IV infusion time calculator (when will the infusion finish?)
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Result
Times are rounded to the nearest minute. For exam practice only. This is a study aid, never a clinical decision: always follow the prescription, local protocols and the product information.
Find out how long an IV infusion will take and at what time it will finish. Enter the volume and either the pump rate in mL/h or the drip rate in drops per minute with the drop factor of the giving set. Add the start time to get the finishing time, including when the infusion runs past midnight. Every step of the calculation is shown, as in nursing dosage exams.
Step-by-step solution
Infusion time = volume ÷ rate
Finishing time = start time + infusion time
Key formulas
- Pump rate
- mL/h = volume (mL)/time (h)
- Drip rate
- drops/min = volume (mL) × drop factor / time (min)
- Infusion time
- time (h) = volume (mL)/rate (mL/h)
How to calculate an IV infusion time
- For a gravity infusion, convert the drip rate to mL/h: gtt/min × 60 ÷ drop factor (gtt/mL).
- Infusion time in hours = volume (mL) ÷ rate (mL/h).
- Convert the decimal part to minutes by multiplying by 60: 6.4 h is 6 h and 0.4 × 60 = 24 min.
- Add the infusion time to the start time to get the finishing time, using the 24-hour clock.
Questions and answers
How do I convert decimal hours to hours and minutes?
Keep the whole hours and multiply the decimal part by 60. For example, 1000 mL at 150 mL/h takes 6.667 h: 6 hours and 0.667 × 60 = 40 minutes.
What is the drop factor?
The number of drops that make 1 mL in a giving set, printed on the package. Macrodrip sets are usually 10, 15 or 20 gtt/mL; microdrip sets are 60 gtt/mL, where gtt/min equals mL/h.
What if the infusion runs past midnight?
The calculator wraps the time around the 24-hour clock and marks it as the next day, or the number of days later for long infusions.
Why might the real time differ?
Gravity infusions slow down or speed up with the position of the patient, the height of the bag and the cannula. Pumps are more accurate, but interruptions and extra doses also change the end time.
Practise it yourself
Practise IV infusion rates
A calculator gives the answer. In the exam you need the method: practise it with new problems, hints and worked solutions.