mg (milligrams)
mcg (micrograms)
g (grams)
mL (milliliters)
Units
mEq (milliequivalents)
mg (milligrams)
mcg (micrograms)
g (grams)
mL (milliliters)
Units
mEq (milliequivalents)
Leave blank if dosage is not weight-based.
Enter a fixed dose if the medication is not dosed per kg.
Your calculated dosage will appear here.
Understanding Medication Dosage Calculations
Accurate medication dosage is critical in healthcare to ensure patient safety and treatment efficacy. This calculator helps to determine the correct amount of medication to administer based on patient weight, medication concentration, and prescribed dosage guidelines.
Why is Dosage Calculation Important?
Patient Safety: Underdosing can lead to ineffective treatment, while overdosing can cause severe toxicity and adverse effects.
Treatment Efficacy: Correct dosing ensures the medication reaches therapeutic levels in the body to combat illness.
Individualized Care: Many medications are dosed based on factors like weight, age, and organ function, requiring precise calculations.
How This Calculator Works
This calculator employs standard pharmaceutical calculation principles. The core logic involves:
Weight-Based Dosing: If a "Dosage per kg" is provided, the calculator multiplies this by the patient's weight (in kg) to determine the total required dose in the desired unit.
Total Dose = Patient Weight (kg) × Dosage per kg (e.g., mg/kg)
Fixed Dosing: If a "Fixed Dosage" is provided (and "Dosage per kg" is not), this value is used directly as the total required dose. This is common for certain medications where a standard dose is given regardless of weight.
Concentration Conversion: Once the total required dose is determined (either weight-based or fixed), the calculator uses the medication's concentration to figure out the volume (usually mL) to administer. The formula depends on how the concentration is expressed. For example, if the concentration is given as X mg / Y mL:
Volume to Administer (mL) = (Total Dose (mg) × Volume (mL)) / Concentration (mg)
If the concentration is given as Z units / mL, and the desired dose is in units:
Volume to Administer (mL) = Total Dose (units) / Concentration (units/mL)
Understanding the Inputs:
Patient Weight (kg): Essential for weight-based dosing calculations.
Medication Name: For identification purposes.
Medication Strength Unit: Specifies the unit of measurement for the medication's potency (e.g., mg, mcg, Units).
Concentration: How much of the active ingredient is present in a specific volume or unit of the medication. This is crucial for converting the calculated dose into a measurable volume. Examples include "250 mg/5 mL" for liquid suspensions or "100 units/mL" for insulin.
Desired Dosage Unit: The unit in which the final dosage should be expressed (e.g., mg, mL).
Desired Dosage per kg: The prescribed amount of medication per kilogram of patient weight. This is common for many antibiotics, sedatives, and chemotherapy agents.
Fixed Dosage: A set dose that does not depend on patient weight. This is used when a specific, non-weight-adjusted dose is prescribed.
Disclaimer:
This calculator is intended for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or medication. Never disregard professional medical advice or delay in seeking it because of something you have read on this calculator or its accompanying information. Healthcare professionals should always use their clinical judgment and verify calculations with official drug references and institutional protocols.
function calculateDosage() {
var patientWeightKg = parseFloat(document.getElementById("patientWeightKg").value);
var medicationName = document.getElementById("medicationName").value.trim();
var strengthUnit = document.getElementById("strengthUnit").value;
var concentrationInput = document.getElementById("concentration").value.trim();
var dosageUnit = document.getElementById("dosageUnit").value;
var dosagePerKg = parseFloat(document.getElementById("dosagePerKg").value);
var fixedDosage = parseFloat(document.getElementById("fixedDosage").value);
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = 'Your calculated dosage will appear here.'; // Reset result
// — Input Validation —
if (isNaN(patientWeightKg) || patientWeightKg mg)
requiredDoseUnit = dosageUnit;
} else if (!isNaN(fixedDosage)) {
// Fixed dosing
totalRequiredDose = fixedDosage;
requiredDoseUnit = dosageUnit;
} else {
// Should not happen due to validation, but as a safeguard
resultDiv.innerHTML = "Error in dosage type.";
return;
}
// — Unit Conversion (Basic) —
// For simplicity, we'll handle common conversions like mcg to mg, g to mg.
// A full system would require a comprehensive unit conversion library.
var normalizedTotalDose = totalRequiredDose;
var normalizedConcentrationValue = concentrationValue;
var normalizedConcentrationDosageUnit = concentrationDosageUnit;
var normalizedRequiredDoseUnit = requiredDoseUnit;
// Convert concentration dosage unit to the desired dosage unit for calculation
if (normalizedConcentrationDosageUnit !== normalizedRequiredDoseUnit) {
if (normalizedConcentrationDosageUnit === 'mcg' && normalizedRequiredDoseUnit === 'mg') {
normalizedConcentrationValue /= 1000;
normalizedConcentrationDosageUnit = 'mg';
} else if (normalizedConcentrationDosageUnit === 'mg' && normalizedRequiredDoseUnit === 'mcg') {
normalizedConcentrationValue *= 1000;
normalizedConcentrationDosageUnit = 'mcg';
} else if (normalizedConcentrationDosageUnit === 'g' && normalizedRequiredDoseUnit === 'mg') {
normalizedConcentrationValue *= 1000;
normalizedConcentrationDosageUnit = 'mg';
} else if (normalizedConcentrationDosageUnit === 'mg' && normalizedRequiredDoseUnit === 'g') {
normalizedConcentrationValue /= 1000;
normalizedConcentrationDosageUnit = 'g';
}
// Add more conversions as needed (e.g., mEq, Units) – these often don't have direct linear conversions without more info
}
// Convert total required dose to match the concentration's dosage unit for calculation
if (normalizedRequiredDoseUnit !== normalizedConcentrationDosageUnit) {
if (normalizedRequiredDoseUnit === 'mcg' && normalizedConcentrationDosageUnit === 'mg') {
normalizedTotalDose *= 1000;
} else if (normalizedRequiredDoseUnit === 'mg' && normalizedConcentrationDosageUnit === 'mcg') {
normalizedTotalDose /= 1000;
} else if (normalizedRequiredDoseUnit === 'g' && normalizedConcentrationDosageUnit === 'mg') {
normalizedTotalDose /= 1000;
} else if (normalizedRequiredDoseUnit === 'mg' && normalizedConcentrationDosageUnit === 'g') {
normalizedTotalDose *= 1000;
}
// Adjust the required unit after conversion if necessary
// normalizedRequiredDoseUnit = normalizedConcentrationDosageUnit; // This might be needed if we force calculation unit
}
// — Volume Calculation —
var volumeToAdminister = NaN;
if (concentrationVolumeUnit === 'mL') {
// Standard formula: (Total Dose * Volume) / Concentration Value
// Example: (500 mg * 5 mL) / 250 mg = 10 mL
if (normalizedConcentrationValue > 0) {
volumeToAdminister = (normalizedTotalDose * (concentrationInput.includes('/5') ? 5 : (concentrationInput.includes('/10') ? 10 : (concentrationInput.includes('/3') ? 3 : (concentrationInput.includes('/1') ? 1 : (concentrationInput.includes('/60') ? 60 : 5))))) ) / normalizedConcentrationValue; // Simplified volume extraction
// A more robust parser would extract the volume number accurately. Here we guess based on common values.
// Let's refine volume extraction:
var volumeNumberMatch = concentrationInput.replace(/\s+/g, ").split('/')[1].match(/^(\d+(\.\d+)?)/);
var actualVolume = 1; // Default to 1 if parsing fails
if (volumeNumberMatch && volumeNumberMatch[1]) {
actualVolume = parseFloat(volumeNumberMatch[1]);
}
volumeToAdminister = (normalizedTotalDose * actualVolume) / normalizedConcentrationValue;
} else {
resultDiv.innerHTML = "Concentration value cannot be zero.";
return;
}
} else {
// Handle other volume units if necessary, or state unsupported
resultDiv.innerHTML = "Only mL volume unit is currently supported for calculation.";
return;
}
// Final check for calculation validity
if (isNaN(volumeToAdminister) || !isFinite(volumeToAdminister)) {
resultDiv.innerHTML = "Calculation resulted in an invalid value. Please check your inputs.";
return;
}
// — Display Result —
var displayDoseValue = totalRequiredDose;
var displayDoseUnit = requiredDoseUnit;
// Format the results nicely
var formattedDose = parseFloat(displayDoseValue.toFixed(2)); // Round to 2 decimal places
var formattedVolume = parseFloat(volumeToAdminister.toFixed(2)); // Round volume
resultDiv.innerHTML = "For " + medicationName + ", administer:" +
"" + formattedDose + " " + displayDoseUnit + "" +
"(This corresponds to " + formattedVolume + " mL)";
}