10 gtt/mL (Macro)
15 gtt/mL (Macro)
20 gtt/mL (Macro)
60 gtt/mL (Micro)
Check your IV tubing package for this number.
function calculateIVRate() {
var volumeInput = document.getElementById('ivVolume');
var timeInput = document.getElementById('ivTime');
var timeUnitInput = document.getElementById('ivTimeUnit');
var dropFactorInput = document.getElementById('ivDropFactor');
var resultDiv = document.getElementById('ivResult');
var volume = parseFloat(volumeInput.value);
var time = parseFloat(timeInput.value);
var timeUnit = timeUnitInput.value;
var dropFactor = parseFloat(dropFactorInput.value);
if (isNaN(volume) || isNaN(time) || volume <= 0 || time <= 0) {
resultDiv.style.display = 'block';
resultDiv.innerHTML = 'Please enter valid positive numbers for Volume and Time.';
return;
}
// Convert time to minutes and hours for different calculations
var totalMinutes = 0;
var totalHours = 0;
if (timeUnit === 'hours') {
totalMinutes = time * 60;
totalHours = time;
} else {
totalMinutes = time;
totalHours = time / 60;
}
// Calculation Logic
// 1. Flow Rate in mL/hr
var mlPerHour = volume / totalHours;
// 2. Drip Rate in gtt/min (Formula: (Volume in mL * Drop Factor) / Time in Minutes)
var gttPerMin = (volume * dropFactor) / totalMinutes;
// Formatting results
// mL/hr typically rounded to 1 decimal place for electronic pumps
var displayMlPerHour = Math.round(mlPerHour * 10) / 10;
// Drops per minute must be a whole number (you cannot count partial drops manually)
var displayGttPerMin = Math.round(gttPerMin);
resultDiv.style.display = 'block';
resultDiv.innerHTML =
'
Calculation Results
' +
'
Flow Rate: ' + displayMlPerHour + ' mL/hr
' +
'
Drip Rate: ' + displayGttPerMin + ' gtt/min
' +
" +
'Based on ' + volume + ' mL over ' + time + ' ' + timeUnit + ' with a drop factor of ' + dropFactor + ' gtt/mL.';
}
How to Calculate Rate of IV Infusion
Calculating the correct intravenous (IV) infusion rate is a fundamental skill in nursing and pharmacology. Accurate calculations ensure that patients receive the prescribed amount of fluid or medication over a specific period, preventing complications such as fluid overload or under-dosing. This guide breaks down the essential formulas and steps used to calculate flow rates in mL/hour and drip rates in drops per minute (gtt/min).
Key Terms Needed for Calculation
Total Volume: The amount of fluid to be infused, usually measured in milliliters (mL).
Time: The duration over which the fluid must be infused, measured in hours or minutes.
Drop Factor (gtt/mL): The number of drops required to make 1 mL of fluid. This is determined by the tubing size.
Macrodrip: Typically 10, 15, or 20 gtt/mL. Used for general infusions.
Microdrip: Always 60 gtt/mL. Used for pediatric or precise medication administration.
Formula 1: Calculating Flow Rate (mL/hr)
This calculation is used primarily when setting up an electronic infusion pump, which requires the rate to be programmed in milliliters per hour.
Flow Rate (mL/hr) = Total Volume (mL) ÷ Time (hours)
Example: A doctor prescribes 1000 mL of Normal Saline to infuse over 8 hours. Calculation: 1000 mL ÷ 8 hours = 125 mL/hr.
Formula 2: Calculating Drip Rate (gtt/min)
When an electronic pump is not available, nurses must manually regulate the flow using the roller clamp on the IV tubing. To do this, you must calculate how many drops should fall into the drip chamber per minute.
Drip Rate (gtt/min) = (Total Volume (mL) × Drop Factor (gtt/mL)) ÷ Time (minutes)
Example: You need to infuse 1000 mL over 8 hours using tubing with a drop factor of 15 gtt/mL.
Inaccurate IV rates can lead to serious patient harm. An infusion running too fast (bolus) can cause heart failure or pulmonary edema, while an infusion running too slow can result in dehydration or inadequate therapeutic levels of medication. Always double-check your math, and when in doubt, have a second nurse verify your calculations.