Please enter a valid volume and time duration greater than zero.
Calculated Flow Rate0 mL/hr
function calculateFlowRate() {
// 1. Get input values
var volumeInput = document.getElementById('totalVolume').value;
var hoursInput = document.getElementById('durationHours').value;
var minutesInput = document.getElementById('durationMinutes').value;
// 2. Parse values to floats
var volume = parseFloat(volumeInput);
var hours = parseFloat(hoursInput);
var minutes = parseFloat(minutesInput);
// 3. Handle empty inputs (treat as 0)
if (isNaN(hours)) hours = 0;
if (isNaN(minutes)) minutes = 0;
// 4. Validation
var errorDiv = document.getElementById('errorDisplay');
var resultDiv = document.getElementById('flowResultContainer');
if (isNaN(volume) || volume <= 0) {
errorDiv.style.display = 'block';
errorDiv.innerHTML = "Please enter a positive Total Volume in mL.";
resultDiv.style.display = 'none';
return;
}
// Calculate total time in hours
var totalTimeInHours = hours + (minutes / 60);
if (totalTimeInHours <= 0) {
errorDiv.style.display = 'block';
errorDiv.innerHTML = "Total duration must be greater than 0.";
resultDiv.style.display = 'none';
return;
}
// 5. Calculate Flow Rate
// Formula: Volume (mL) / Time (hr)
var flowRate = volume / totalTimeInHours;
// Rounding logic (standard medical practice is usually nearest whole number or 1 decimal)
// We will show 1 decimal place for precision.
var formattedRate = flowRate.toFixed(1);
// 6. Display Results
errorDiv.style.display = 'none';
resultDiv.style.display = 'block';
document.getElementById('resultValue').innerHTML = formattedRate + ' mL/hr';
document.getElementById('resultExplanation').innerHTML =
"To infuse " + volume + " mL over " + hours + " hr " + minutes + " min, set the pump to " + formattedRate + " mL/hr.";
}
How to Calculate the Flow Rate in mL/hr
In clinical settings, calculating the correct IV flow rate is a fundamental skill for nurses, pharmacists, and medical professionals. While modern infusion pumps often handle the mechanics, understanding how to calculate the flow rate in mL/hr manually is critical for verification, safety, and situations where automated pumps are unavailable.
The flow rate in milliliters per hour (mL/hr) determines the speed at which a volume of fluid is administered intravenously to a patient. This metric is essential for ensuring medications are delivered at a therapeutic rate without causing volume overload.
The Formula
The basic formula to calculate the flow rate in mL/hr is straightforward. You are simply dividing the total volume of fluid by the total time of infusion in hours.
Flow Rate (mL/hr) = Total Volume (mL) ÷ Total Time (hours)
Step-by-Step Calculation Guide
Identify the Total Volume: Determine the total amount of fluid ordered by the physician, measured in milliliters (mL).
Identify the Total Time: Determine the duration over which the infusion must be delivered. If the time is given in minutes, you must convert it to hours.
Convert Minutes to Hours (if necessary): Divide the number of minutes by 60. For example, 30 minutes = 0.5 hours.
Divide: Divide the Total Volume by the Total Time (in hours).
Practical Examples
Example 1: Standard Infusion
Scenario: A doctor orders 1,000 mL of Normal Saline to be infused over 8 hours.
Total Volume = 1,000 mL
Total Time = 8 hours
Calculation: 1,000 ÷ 8 = 125
Result: 125 mL/hr
Example 2: Short Duration (Antibiotics)
Scenario: A patient requires 100 mL of an antibiotic solution infused over 30 minutes.
Total Volume = 100 mL
Total Time = 30 minutes
Convert Time: 30 ÷ 60 = 0.5 hours
Calculation: 100 ÷ 0.5 = 200
Result: 200 mL/hr
Why Precision Matters
When learning how to calculate the flow rate in mL/hr, precision is vital. While many infusion pumps allow for decimal inputs (e.g., 83.3 mL/hr), others may require rounding to the nearest whole number. Always follow your facility's specific protocols regarding rounding and significant figures.
Furthermore, calculating mL/hr is different from calculating the drip rate (gtt/min). The flow rate (mL/hr) is used for electronic infusion pumps, whereas the drip rate is used for manual gravity tubing based on the tubing's drop factor. Ensure you are using the correct formula for the equipment you are using.