Enter the volume in the bag and the pump rate to get the running time. See the infusion-time formula for the method.
Infusion time
8 hr
1. Divide the volume by the rate
1000 mL ÷ ( 125 mL ÷ 1 hr )
2. Cancel mL and solve for hours
= 1000 ÷ 125 hr
= 8 hr
3. Convert the decimal hours to hours and minutes
8 hr = 8 hr
= 8 hr
How it works
Dividing the volume by the hourly rate cancels mL and leaves hours:
Infusion time (hr) = volume (mL) ÷ rate (mL/hr)
The decimal hours are then converted to hours and minutes by multiplying the decimal part by 60. The full method, with practice problems, is in the IV infusion time lesson.
Worked example
An IV pump is running 1000 mL of lactated Ringer's at 125 mL/hr. How long will the infusion take?
Answer: 8 hr
1. Divide the volume by the rate
1000 mL ÷ ( 125 mL ÷ 1 hr )
2. Cancel mL and solve for hours
= 1000 ÷ 125 hr
= 8 hr
3. Convert the decimal hours to hours and minutes
8 hr = 8 hr
= 8 hr
Frequently asked questions
What is the infusion time formula?
Infusion time (hr) = volume (mL) divided by rate (mL/hr). For example, 1000 mL at 125 mL/hr runs for 1000 / 125 = 8 hours.
How do I convert decimal hours to hours and minutes?
Multiply the decimal part by 60. For example, 2.5 hr is 2 hr plus 0.5 x 60 = 30 min, so 2 hr 30 min. The calculator shows this breakdown automatically.
Why does infusion time matter clinically?
Knowing when a bag will run out lets the nurse plan the next bag, schedule assessments, and chart an accurate completion time for the infusion.