# Calculate IV rate as gtt/min

## Formulas

To calculate rate as drops/minute (gtt/min) using minutes:

$\frac{V×C}{M}$
• V = Volume
• C = Calibration
• M = Minutes

To calculate rate as gtt/min using hours:

$\frac{V×C}{\left(H×\mathrm{60 min}\right)}$
• V = Volume
• C = Calibration
• H = Hours

To convert milliliters/hour (mL/hr) to gtt/min:

$\frac{R×C}{\mathrm{60 min}}$
• R = Rate
• C = Calibration

## Examples

1. Give a 50 milliliter (mL) IVPB over 30 minutes using IV tubing with a calibration of 10 drops/milliliter (gtt/mL).  How many drops per minute should this IVPB be set for?

• Volume = 50 mL
• Calibration = 10
• Minutes = 30 min
$\frac{\mathrm{50 mL}×\mathrm{10}}{\mathrm{30 min}}$

The answer is 16.7 or 70 gtt/min.

2. Using IV tubing alone (calibrated at 60 gtt/mL), prepare an IV to infuse 1 liter over 8 hours.  How many drops per minute should the IV be set for?

• Volume = 1000 mL
• Calibration = 60
• Hours = 8
$\frac{\mathrm{1000 mL}×\mathrm{60}}{\left(8×\mathrm{60 min}\right)}$

The answer is 125 gtt/min.

💡 Note, when using microdrip tubing (calibration = 60), the drip rate will be the same as mL/hr.  This will save you the time of calculating the drip rate if asked to give the rate in mL/hr.

3. The doctor orders an IV to infuse at 125 mL/hr. Calculate the flow rate using 10 gtt/mL tubing.

• Rate = 125
• Calibration = 10
$\frac{\mathrm{125}×\mathrm{10}}{\mathrm{60 min}}$

The answer is 20.8 or 21 gtt/min.

You may be wondering why a second answer is displayed in the calculator. The first answer displays the number of drops per minute. The second answer displays how many drops fall in 15 seconds. Sometimes the IV rate is set by counting for 15 seconds instead of a full minute. It's not as accurate.