Calculate mL/hr flow rate based on dose, weight, and concentration.
1. Patient Parameter
2. Ordered Dose
mcg (micrograms)
mg (milligrams)
g (grams)
units
mEq
per Minute (/min)
per Hour (/hr)
3. IV Bag / Concentration
mg (milligrams)
mcg (micrograms)
g (grams)
units
mEq
Required Flow Rate
0 mL/hr
function toggleWeightInput() {
var isChecked = document.getElementById('isWeightBased').checked;
var container = document.getElementById('weightContainer');
if(isChecked) {
container.style.display = 'block';
} else {
container.style.display = 'none';
}
}
function calculateInfusionRate() {
// Clear previous results
document.getElementById('resultBox').style.display = 'none';
document.getElementById('errorMsg').style.display = 'none';
// 1. Get Inputs
var isWeightBased = document.getElementById('isWeightBased').checked;
var weight = parseFloat(document.getElementById('patientWeight').value);
var doseAmount = parseFloat(document.getElementById('doseAmount').value);
var doseUnit = document.getElementById('doseUnitPrefix').value;
var doseTime = document.getElementById('doseTime').value;
var bagAmount = parseFloat(document.getElementById('bagAmount').value);
var bagUnit = document.getElementById('bagUnitPrefix').value;
var bagVolume = parseFloat(document.getElementById('bagVolume').value);
// 2. Validation
if (isNaN(doseAmount) || isNaN(bagAmount) || isNaN(bagVolume)) {
showError("Please fill in all numeric fields correctly.");
return;
}
if (isWeightBased && (isNaN(weight) || weight <= 0)) {
showError("Please enter a valid patient weight.");
return;
}
if (bagVolume <= 0) {
showError("Bag volume must be greater than zero.");
return;
}
// Unit compatibility check
var massUnits = ['mcg', 'mg', 'g'];
var otherUnits = ['units', 'mEq'];
var doseIsMass = massUnits.indexOf(doseUnit) !== -1;
var bagIsMass = massUnits.indexOf(bagUnit) !== -1;
if (doseIsMass !== bagIsMass) {
if (!doseIsMass && doseUnit !== bagUnit) {
showError("Dose unit and Bag unit must match (e.g., both must be Units or mEq).");
return;
}
if (doseIsMass && !bagIsMass) {
showError("Cannot convert mass units (mg/mcg/g) to " + bagUnit);
return;
}
}
if (!doseIsMass && doseUnit !== bagUnit) {
showError("Dose unit ("+doseUnit+") and Bag unit ("+bagUnit+") do not match.");
return;
}
// 3. Normalization (Convert everything to mg or units/mEq)
// Conversion factors to mg
function toMg(val, unit) {
if (unit === 'mcg') return val / 1000;
if (unit === 'mg') return val;
if (unit === 'g') return val * 1000;
return val; // Should not happen for mass logic
}
var normalizedDose = doseAmount;
var normalizedBag = bagAmount;
// If working with mass, convert both to mg for calculation
if (doseIsMass) {
normalizedDose = toMg(doseAmount, doseUnit);
normalizedBag = toMg(bagAmount, bagUnit);
}
// If units/mEq, they are already equal numbers (e.g. 5 units dose, 500 units bag)
// because we checked they are the same type above.
// 4. Calculate Total Dose Per Hour
var dosePerHour = normalizedDose;
// Adjust for time
if (doseTime === 'min') {
dosePerHour = dosePerHour * 60;
}
// Adjust for weight
if (isWeightBased) {
dosePerHour = dosePerHour * weight;
}
// 5. Calculate Concentration (Amount per mL)
var concentration = normalizedBag / bagVolume; // mg/mL or units/mL
// 6. Calculate Rate (mL/hr)
// Rate = (Dose/hr) / (Concentration/mL)
var rate = dosePerHour / concentration;
// 7. Display Result
var displayRate = rate.toFixed(2);
// Sanity check for infinity
if (!isFinite(rate)) {
showError("Calculation resulted in an invalid number. Check inputs.");
return;
}
document.getElementById('finalRate').innerText = displayRate + " mL/hr";
// Show concentration for verification
var concUnit = doseIsMass ? "mg" : bagUnit;
document.getElementById('concentrationDisplay').innerText =
"Concentration: " + concentration.toFixed(4) + " " + concUnit + "/mL";
document.getElementById('resultBox').style.display = 'block';
}
function showError(msg) {
var err = document.getElementById('errorMsg');
err.innerText = msg;
err.style.display = 'block';
}
Understanding Dosage Calculation Infusion Rates
In critical care and nursing, accurately calculating the infusion rate of intravenous (IV) medications is a fundamental skill. Errors in these calculations can lead to under-dosing or life-threatening overdoses. This calculator utilizes standard dimensional analysis to convert orders (like mcg/kg/min) into actionable pump settings (mL/hr).
The Universal Formula
To determine the flow rate in mL/hr, you generally need three key components: the patient's weight (if the dose is weight-based), the ordered dose, and the concentration of the medication available in the IV bag.
If you are calculating manually, follow these steps to ensure accuracy:
Step 1: Convert Units. Ensure your ordered dose and the drug available are in the same units (e.g., convert grams to milligrams).
Step 2: Calculate Total Hourly Dose.
If the order is per minute, multiply by 60.
If the order is weight-based (per kg), multiply by the patient's weight in kg.
Step 3: Determine Concentration. Divide the total amount of drug in the bag by the total volume of fluid (Amount / Volume).
Step 4: Divide. Divide the Total Hourly Dose (Step 2) by the Concentration (Step 3).
Example: Dopamine Calculation
Imagine a doctor orders Dopamine at 5 mcg/kg/min for a patient weighing 70 kg. The pharmacy sends a bag containing 400 mg of Dopamine in 250 mL of D5W.
Convert Dose to mg/hr: 5 mcg * 70 kg * 60 min = 21,000 mcg/hr. 21,000 mcg = 21 mg/hr.
Calculate Concentration: 400 mg / 250 mL = 1.6 mg/mL.
When performing dosage calculations, always keep these standard conversions in mind:
1 g (gram) = 1,000 mg (milligrams)
1 mg (milligram) = 1,000 mcg (micrograms)
1 kg (kilogram) = 2.2 lbs (pounds)
Safety Warning
This calculator is for educational and verification purposes only. In a clinical setting, all IV pump settings and dosage calculations should be double-checked by a second qualified healthcare professional according to facility protocols. Never rely solely on a web-based calculator for patient care decisions.