Drug Dose by BSA Calculator

Enter patient weight, height, and protocol dose rate to calculate total drug dose by body surface area.

Created by Luis GonzalezLast updated: May 9, 2026

How to Use This Calculator

1
Enter patient's weight
Input the patient's body weight in kilograms (kg), which is a key factor for BSA calculation.
2
Provide patient's height
Input the patient's height in centimeters (cm), necessary for all BSA formulas.
3
Specify the dose rate
Enter the prescribed dose in milligrams per square meter (mg/m²) as per the drug protocol.
4
Select a BSA formula
Choose between Mosteller, Du Bois, or Haycock formulas, depending on clinical preference or protocol.
5
Review your results
The calculator provides the total drug dose, calculated body surface area, dose per kilogram, and other relevant metrics.

Example Calculation

An oncologist needs to calculate a chemotherapy dose for a patient weighing 70 kg and standing 170 cm tall, with a prescribed dose rate of 100 mg/m², using the Mosteller formula.

Weight (kg)

70 kg

Height (cm)

170 cm

Dose Rate (mg/m²)

100 mg/m²

BSA Formula

Mosteller

Results

181.82 mg

Tips

Verify BSA Formula Choice

Ensure you select the correct BSA formula as different formulas can yield slightly different BSA values, which directly impacts the calculated dose. Mosteller is widely used, but specific protocols might mandate Du Bois or Haycock.

Consider BSA Capping

For obese patients, consider using a capped BSA (typically 2.0 m²) to prevent excessive dosing, especially for highly toxic drugs like certain chemotherapeutics. The calculator provides a 'Capped Dose' output for this reason.

Accurate Height and Weight

Use precise and recent height and weight measurements. Errors in these inputs can lead to significant dosing inaccuracies, potentially resulting in under-treatment or increased toxicity, particularly with narrow therapeutic index drugs.

Precision Dosing with the Drug Dose by BSA Calculator

The Drug Dose by BSA Calculator is an essential tool for healthcare professionals, particularly in oncology, to determine precise medication dosages based on a patient's Body Surface Area. This method accounts for individual physiological variations more accurately than weight-based dosing alone, ensuring that patients receive the optimal amount of medication. Calculating a dose based on BSA (e.g., a 70 kg, 170 cm patient might have a BSA of 1.82 m², leading to a 182 mg dose at 100 mg/m²) is a standard practice for numerous potent drugs in 2025.

Comparing BSA Formulas: Mosteller, Du Bois, and Haycock

The calculation of Body Surface Area (BSA) is central to many drug dosing regimens, particularly for chemotherapy. While the underlying concept is consistent, several formulas exist, each with slight variations in their derivation and applicability. The calculator offers three prominent options: Mosteller, Du Bois, and Haycock.

The Mosteller formula is widely used due to its simplicity:

BSA (m²) = sqrt((Weight (kg) × Height (cm)) / 3600)

The Du Bois formula is another common method, often considered robust:

BSA (m²) = 0.007184 × Weight (kg)^0.425 × Height (cm)^0.725

The Haycock formula offers a third alternative:

BSA (m²) = 0.024265 × Weight (kg)^0.5378 × Height (cm)^0.3964

Each formula uses a patient's weight and height, but the exponents and constants differ, leading to slight variations in the calculated BSA. Clinicians typically choose a formula based on institutional protocols or specific drug guidelines, which may have validated one formula over others for particular patient populations or drug classes.

💡 For drugs requiring renal dose adjustments, our eGFR for Drug Dosing Calculator can provide crucial kidney function estimates to complement BSA-based calculations.

Calculating a Chemotherapy Dose for an Adult Patient

Imagine an oncology patient who weighs 70 kg and is 170 cm tall, prescribed a chemotherapy agent at a dose rate of 100 mg/m². The hospital protocol specifies using the Mosteller formula for BSA calculation.

Calculate Body Surface Area using Mosteller formula: BSA = sqrt((70 kg × 170 cm) / 3600) BSA = sqrt(11900 / 3600) BSA = sqrt(3.30555) BSA ≈ 1.818 m²
Calculate the total drug dose: Total Dose = BSA × Dose Rate Total Dose = 1.818 m² × 100 mg/m² Total Dose ≈ 181.8 mg

Therefore, the patient would receive a total dose of approximately 181.8 mg of the chemotherapy agent.

💡 To understand how the drug will be eliminated from the body over time, which can influence subsequent dosing, consider using our First-Order Elimination Calculator.

Oncology Dosing and BSA Capping Considerations

In oncology, precise dosing based on Body Surface Area (BSA) is paramount for maximizing efficacy while minimizing severe toxicity. Many chemotherapeutic agents, such as doxorubicin or paclitaxel, have narrow therapeutic windows, meaning small deviations from the optimal dose can have significant consequences. For obese patients, BSA calculations can sometimes overestimate the true drug distribution volume, potentially leading to overdosing. To counteract this, many protocols implement "BSA capping," where the BSA is limited to a maximum value, often 2.0 m² or 2.2 m². This adjustment prevents excessive dosing and reduces the risk of dose-related toxicities without compromising anti-tumor activity. Accurate height and weight measurements are always critical, as even minor errors can lead to substantial dosing discrepancies for potent agents.

Key Meteorological Benchmarks for Humidity and Comfort

Pharmacists, physicians, and other healthcare professionals routinely interpret BSA-derived drug doses. They critically assess the calculated "Total Dose" against established guidelines and the patient's individual clinical status. For instance, a dose that falls significantly outside the expected range for a given drug and indication (e.g., a calculated dose of 500 mg for a drug typically given at 150-200 mg) would immediately trigger a review of the inputs and the rationale. The "Body Surface Area" value itself provides context; a very low BSA (e.g., <1.5 m²) might indicate a frail or underweight patient, prompting a re-evaluation of the dose rate or consideration of dose reductions. Furthermore, the "Capped Dose" output is closely scrutinized for obese patients, as practitioners must decide whether to use the uncapped or capped dose based on the specific drug, patient comorbidities, and institutional policy, always aiming for the best balance between efficacy and safety.

Frequently Asked Questions

What is Body Surface Area (BSA) and why is it used for drug dosing?

Body Surface Area (BSA) is a measure of the total surface area of a person's body, expressed in square meters (m²), and is widely used for drug dosing, especially in oncology. It is believed to correlate better with metabolic rate and drug clearance than body weight alone, providing a more consistent and individualized dosing approach for many potent medications.

Which BSA formula is generally preferred?

The Mosteller formula is one of the most commonly used and widely accepted BSA calculation methods in clinical practice due to its simplicity and accuracy across various patient populations. However, specific clinical protocols or drug guidelines may recommend other formulas like Du Bois or Haycock, often for particular patient demographics or drug types.

What is 'BSA capping' and when is it necessary?

BSA capping is the practice of limiting the calculated Body Surface Area to a maximum value, typically 2.0 m² or 2.2 m², for drug dosing in obese patients. This practice is necessary to prevent potential overdosing and increased toxicity, as BSA calculations can overestimate drug distribution volume in individuals with extreme obesity, leading to disproportionately high doses.