IV Infusion Calculator
Two Views of the Same Infusion
An infusion order can be expressed two ways — as a flow rate in milliliters per hour, which is what an electronic pump is programmed with, or as a drip rate in drops per minute, which is what a manual gravity set is regulated by. This calculator produces both from the same volume-and-time inputs, so the numbers stay consistent regardless of which delivery method is being used.
The Formula
Flow Rate (mL/hr) = Total Volume (mL) ÷ Time (hr)
Drip Rate (gtt/min) = (Total Volume (mL) × Drop Factor (gtt/mL)) ÷ Time (min)
Drip Rate (gtt/min) = (Total Volume (mL) × Drop Factor (gtt/mL)) ÷ Time (min)
Worked Example
1000 mL infused over 8 hours: the flow rate is 1000 ÷ 8 = 125 mL/hr. With a 15 gtt/mL set, the equivalent drip rate is (1000 × 15) ÷ 480 = 31.3 gtt/min.
Why Both Numbers Together
- Switching between pump and gravity delivery — if a pump fails or isn't available, the drip rate lets staff continue the same infusion manually without recalculating from scratch.
- Programming an infusion pump — pumps are set directly in mL/hr, making the flow rate the number that actually gets entered into the device.
- Order verification — comparing the calculated flow rate against a physician's order is a routine safety check before starting an infusion.
Note: Always confirm the drop factor printed on the specific administration set being used — common values are 10, 15, 20, and 60 gtt/mL, and using the wrong one will produce an incorrect drip rate even if the underlying flow rate is correct.
How to Use This Calculator
- Enter the total volume to be infused, in mL.
- Enter the time value.
- Select whether that time is in hours or minutes.
- Select the drop factor of the administration set.
- Select Calculate to see both the flow rate (mL/hr) and drip rate (gtt/min).
Related Calculations
For drip rate alone from a fixed time value, see the Drip Rate Calculator, or track intake and output with the Fluid Balance Calculator.