IV Flow Rate Calculator
Calculate the manual infusion rate in drops per minute (gtt/min).
Hours
Minutes
10 gtt/mL (Macro)
15 gtt/mL (Macro)
20 gtt/mL (Macro)
60 gtt/mL (Micro)
Check the IV tubing package for the drop factor.
The required flow rate is:
drops per minute (gtt/min)
How to Calculate Drops Per Minute (gtt/min)
In clinical settings, calculating the intravenous (IV) flow rate is a critical skill for nursing and medical professionals. When an electronic infusion pump is not available, manual IV sets are used, and the rate must be calculated based on the number of drops that fall into the drip chamber per minute.
The IV Flow Rate Formula
To find the flow rate in drops per minute, use the following standard formula:
(Total Volume in mL × Drop Factor) / Total Time in Minutes = Flow Rate (gtt/min)
Key Components Defined
- Total Volume: The total amount of fluid or medication to be infused, measured in milliliters (mL).
- Drop Factor: The number of drops required to deliver 1 mL of fluid. This is determined by the size of the IV tubing. Common factors include 10, 15, or 20 (macrodrip) and 60 (microdrip).
- Time: The duration over which the infusion should run, converted into minutes.
Common Drop Factors
| Tubing Type | Drop Factor (gtt/mL) | Typical Use Case |
|---|---|---|
| Macrodrip | 10, 15, or 20 | General adult infusions, rapid fluid replacement. |
| Microdrip | 60 | Pediatric patients, precise medication titration, slow rates. |
Step-by-Step Example
Scenario: A physician orders 500 mL of Normal Saline to be infused over 4 hours. Your tubing has a drop factor of 15 gtt/mL.
- Identify Volume: 500 mL
- Convert Time: 4 hours × 60 minutes = 240 minutes
- Identify Drop Factor: 15 gtt/mL
- Apply Formula: (500 × 15) / 240 = 7,500 / 240 = 31.25 gtt/min
In practice, you would round this to 31 drops per minute and monitor the drip chamber with a watch.
Practical Tips for Manual Infusions
- Rounding: Since you cannot count a fraction of a drop, always round the final answer to the nearest whole number.
- Re-checking: Rates can change based on the patient's arm position or the height of the IV bag. Check the drip rate every 15-30 minutes.
- Safety: High-risk medications (like heparin or insulin) should always be administered via an infusion pump rather than manual gravity drip for precision.