IV Infusion Time Calculator
Find how long an IV will take to infuse, and the time it will finish, from the volume and the rate in mL/hr.
Formula
Time (hr) = volume (mL) ÷ rate (mL/hr)
Minutes = decimal part of the hours × 60
How to calculate it step by step
- Divide the volume left to infuse by the rate in mL/hr.
- Keep the whole number as hours.
- Multiply the decimal part by 60 to get the minutes.
- Add the time to the start time to find when the infusion will finish (use 24-hour time to avoid AM/PM errors).
Worked examples
Example 1. 960 mL of D5 0.45% sodium chloride is infusing at 80 mL/hr. How many hours will it take? Answer in hours (for example 2.5).
- Time = volume ÷ rate = 960 mL ÷ 80 mL/hr = 12 hr.
- That is 12 hr.
Answer: 12 hr
Example 2. 480 mL of D5W is infusing at 80 mL/hr. How many hours will it take? Answer in hours (for example 2.5).
- Time = volume ÷ rate = 480 mL ÷ 80 mL/hr = 6 hr.
- That is 6 hr.
Answer: 6 hr
Rounding
Round the final minutes to the nearest whole minute.
Common mistakes
- Writing 6.25 hours as 6 hours 25 minutes: 0.25 hr × 60 is 15 minutes, so 6 hr 15 min.
- Using the total bag volume instead of the volume left to infuse when an infusion is already running.
Nursing safety points
- Set the volume to be infused on the pump so it alarms when the infusion is complete.
- Plan the next bag or the next dose before the current one ends, so the line does not run dry.
Frequently asked questions
How do you calculate how long an IV will take?
Divide the volume by the rate: 1,000 mL at 125 mL/hr takes 1,000 ÷ 125 = 8 hours.
How do you convert decimal hours to minutes?
Multiply the decimal part by 60. For example, 6.25 hours = 6 hours + 0.25 × 60 = 6 hours 15 minutes.