Continuous Infusion Rate Calculator
Calculate intravenous flow rates in mL/hr and gtt/min for clinical accuracy.
How to Calculate Continuous Infusion Rates
Continuous infusion is the controlled administration of fluids or medications over a sustained period. In clinical nursing, calculating the correct flow rate is vital for patient safety and therapeutic efficacy. There are two primary ways to express infusion rates: milliliters per hour (mL/hr) for infusion pumps and drops per minute (gtt/min) for gravity-fed lines.
The Core Formulas
To determine the rates, you must use the following standard medical formulas:
- Flow Rate (mL/hr): Total Volume (mL) ÷ Total Time (hr)
- Drip Rate (gtt/min): [Total Volume (mL) × Drop Factor (gtt/mL)] ÷ Total Time (minutes)
Step-by-Step Example
Suppose a physician orders 1,000 mL of Normal Saline to be infused over 10 hours using a tubing set with a drop factor of 15 gtt/mL.
- Calculate mL/hr: 1,000 mL / 10 hours = 100 mL/hr.
- Convert Hours to Minutes: 10 hours × 60 = 600 minutes.
- Calculate gtt/min: (1,000 mL × 15 gtt/mL) / 600 minutes = 15,000 / 600 = 25 gtt/min.
Key Variables Explained
Total Volume: This is the total amount of fluid in the bag (e.g., 500 mL, 1,000 mL).
Drop Factor: This is determined by the IV tubing used. Macro-drip sets usually deliver 10, 15, or 20 drops per milliliter, while micro-drip sets deliver 60 drops per milliliter.
Infusion Time: The duration over which the fluid must be delivered. This must be converted to minutes when calculating the drip rate.