IV Flow Rate & Drop Rate Calculator
10 gtt/mL (Macro)
15 gtt/mL (Macro)
20 gtt/mL (Macro)
60 gtt/mL (Micro)
Custom…
Volumetric Flow Rate:
0 mL/hr
Drip Rate (Drops per Minute):
0 gtt/min
Total Time in Minutes:
0 min
How to Calculate IV Flow Rates and Dosages
Accurate Intravenous (IV) flow rate calculation is a critical skill in nursing and pharmacology. It ensures that patients receive the prescribed volume of medication or fluid over the correct duration. Whether using an electronic infusion pump or a manual gravity drip set, understanding the underlying math is essential for patient safety.
Understanding the Variables
To calculate the flow rate, you need three specific pieces of information found in the physician's order and on the administration set packaging:
- Total Volume (mL): The amount of fluid to be infused (e.g., 1000 mL Normal Saline).
- Time (Hours/Minutes): The duration over which the fluid must be delivered.
- Drop Factor (gtt/mL): The calibration of the IV tubing, indicating how many drops (guttae) equal 1 milliliter. This is printed on the tubing package.
Formulas for IV Calculations
There are two primary results derived from these calculations: the pump setting (mL/hr) and the manual drip rate (gtt/min).
1. Volumetric Flow Rate (mL/hr)
Used primarily for electronic infusion pumps.
Flow Rate (mL/hr) = Total Volume (mL) ÷ Time (hours)
2. Drop Rate (gtt/min)
Used for manual gravity infusions where the nurse counts drops in the drip chamber.
Drop Rate (gtt/min) = [Total Volume (mL) × Drop Factor (gtt/mL)] ÷ Total Time (minutes)
Common Drop Factors
| Tubing Type | Drop Factor | Typical Usage |
|---|---|---|
| Macrodrip | 10, 15, or 20 gtt/mL | Standard adult infusions, high flow rates, trauma. |
| Microdrip | 60 gtt/mL | Pediatrics, critical care, slow infusion rates. |
Calculation Example
Scenario: A doctor orders 1,000 mL of Lactated Ringer's to be infused over 8 hours. The available tubing has a drop factor of 15 gtt/mL.
Step 1: Calculate mL/hr for a pump.
1000 mL ÷ 8 hours = 125 mL/hr.
Step 2: Calculate gtt/min for manual drip.
First, convert hours to minutes: 8 hours × 60 = 480 minutes.
Formula: (1000 mL × 15 gtt/mL) ÷ 480 min
15,000 ÷ 480 = 31.25
Result: Round to the nearest whole number, 31 gtt/min.