IV Infusion Rate Calculator
Calculate the required mL per hour (mL/hr)
Understanding How to Calculate Hourly Infusion Rate
In clinical settings, accurately calculating the infusion rate is critical for patient safety and therapeutic efficacy. The hourly infusion rate tells a healthcare professional how many milliliters (mL) of a fluid or medication should be administered per hour via an electronic infusion pump.
The Standard Formula for Hourly Infusion Rate
The math behind calculating an infusion rate is straightforward. To find the milliliters per hour (mL/hr), you divide the total volume to be infused by the total time over which it should be administered.
Infusion Rate (mL/hr) = Total Volume (mL) ÷ Total Time (hr)
Calculating When Time is in Minutes
If a medication order specifies a duration in minutes (common for antibiotics), you must first convert the minutes into hours by dividing by 60, or use the modified formula:
Rate (mL/hr) = [Total Volume (mL) ÷ Time (min)] × 60
Clinical Examples
Example 1: Long Duration Maintenance Fluids
A physician orders 1,000 mL of Normal Saline to be infused over 8 hours. What is the hourly rate?
- Total Volume: 1,000 mL
- Total Time: 8 hours
- Calculation: 1,000 ÷ 8 = 125 mL/hr
Example 2: Short Duration Antibiotic
A nurse needs to administer 100 mL of Cefazolin over 30 minutes. What rate should be set on the pump?
- Total Volume: 100 mL
- Total Time: 30 minutes (which is 0.5 hours)
- Calculation: 100 ÷ 0.5 = 200 mL/hr
Important Considerations for IV Infusion
When calculating infusion rates, always keep the following safety checks in mind:
- Pump Precision: Most modern infusion pumps can handle decimal points (e.g., 12.5 mL/hr), but some older equipment might require rounding to the nearest whole number.
- Verification: Always "double-check" calculations, especially for high-alert medications like heparin or insulin, where rates are often weight-based or highly specific.
- Unit Consistency: Ensure the volume is always in milliliters (mL). If the order is in Liters, convert it first (1L = 1,000 mL).
Difference Between Rate and Drip Factor
It is important not to confuse the Hourly Infusion Rate (mL/hr) with the Drip Rate (gtts/min). The hourly rate is used for electronic pumps, while the drip rate is used for gravity infusions where you manually count drops per minute based on the IV tubing's specific drip factor.