# IV Flow Rate Calculator

> Calculate an IV infusion pump rate in mL per hour from the volume and infusion time, with mL per minute and the clock time the infusion will finish.

Category: Healthcare operations · Applies to: Worldwide · Last updated: 2026-10-29
Interactive calculator: https://calculators.geekmidst.com/calculators/iv-flow-rate-calculator

Pump rate in mL/h is the volume divided by the infusion time in hours. It supports, and does not replace, clinical judgement, the prescription and local infusion protocols.

Also called: Infusion rate calculator, mL/hr calculator.

## Inputs
- Volume to infuse (unit mL; default 500)
- Infusion time: hours (unit h; default 4; optional)
- Infusion time: minutes (unit min; default 0; optional)
- Start time (default 08:00; optional)

## Results
- Flow rate
- Flow rate per minute
- Infusion time
- Finishes at

## Formula

```
Flow rate (mL/h) = Volume (mL) ÷ Time (h);  Finish time = Start time + Infusion time
```

Where:
- Volume: fluid to infuse, in mL
- Time: prescribed infusion time

## Worked example
1. Flow rate = 500 mL ÷ 4 h = 125 mL/h.
2. Per minute = 500 ÷ 240 = 2.083 mL/min.
3. Finish = 08:00 + 4 h = 12:00.

**Result:** 500 mL over 4 hours runs at 125 mL/h and, started at 08:00, finishes at 12:00.

## What the result means

Programme the pump with the mL/h rate and the volume to be infused, then confirm against the prescription. For gravity sets, convert to drops per minute with the drip rate calculator.

## Assumptions and limits
- The rate is constant for the whole infusion.
- Line priming volume, interruptions and bag overfill are not included.
- Weight-based or dose-based rates (for example mg/kg/h) are not calculated here.

## Questions

### How do I convert mL/h to drops per minute?

Multiply mL/h by the drop factor and divide by 60. At 125 mL/h on a 10 gtt/mL set that is 20.8, about 21 gtt/min.

### Why might the infusion finish later than shown?

Pauses for alarms, line changes or patient movement add time; the finish time assumes no interruptions.

## Sources
- [Math for Medication Administration (BCcampus open textbook): IV flow rates](https://opentextbc.ca/nursingnumeracy/chapter/iv-flow-rates/)

## Related calculators
- [Infusion Drip Rate Calculator](https://calculators.geekmidst.com/calculators/infusion-drip-rate-calculator)
- [Time Calculator](https://calculators.geekmidst.com/calculators/time-calculator)
- [Hours Calculator](https://calculators.geekmidst.com/calculators/hours-calculator)

_This is a general screening estimate for adults, not medical advice or a diagnosis. Talk to a qualified health professional about your health._

Source: GM¹X CalcVerse — https://calculators.geekmidst.com/calculators/iv-flow-rate-calculator