BSA Dosing Calculator
Calculate body surface area (BSA) and BSA-based drug doses for adults and children using multiple formulas, dose caps, and rounding options.
Clinical use disclaimer
This tool is for educational and research support only. It does not replace clinical judgment, institutional protocols, or official drug labeling.
BSA & Dose Calculator
Typical adult: 40–200 kg; pediatric: 2–100 kg.
Typical adult: 120–220 cm; pediatric: 30–200 cm.
You can compare formulas below after calculation.
If set, effective BSA = min(calculated BSA, cap).
Drug dosing
Enter the protocol-specified dose per m².
If set, total dose will not exceed this value.
Choose rounding that matches vial sizes or institutional policy.
BSA result Primary formula
1.80 m²
Mosteller formula
Dose result
Drug/regimen: –
Dose per m²: – mg/m²
Uncapped dose: – mg
After max-dose cap: – mg
Rounded dose: – mg
BSA formula comparison (same height & weight)
| Formula | BSA (m²) | Difference vs. Mosteller |
|---|
Dosing history (this session)
| Time | Drug / regimen | BSA (m²) | mg/m² | Uncapped (mg) | Capped (mg) | Rounded (mg) |
|---|
What is BSA-based dosing?
Body surface area (BSA) dosing expresses a drug regimen in mg per square meter (mg/m²) of body surface area. The total dose is:
Total dose (mg) = BSA (m²) × dose (mg/m²)
BSA-based dosing is common in oncology (chemotherapy), some immunosuppressants, and other drugs where body size is thought to better reflect drug distribution and clearance than weight alone.
Supported BSA formulas
This calculator can compute BSA using several validated formulas. All assume height in centimeters and weight in kilograms internally (US units are converted automatically).
1. Mosteller formula (default)
BSA (m²) = √( (height(cm) × weight(kg)) / 3600 )
The Mosteller formula is widely used because it is simple and agrees well with more complex formulas across typical adult and pediatric body sizes.
2. DuBois & DuBois
BSA (m²) = 0.007184 × height(cm)0.725 × weight(kg)0.425
One of the earliest BSA formulas, derived from direct surface area measurements in a small adult sample.
3. Haycock (often used in pediatrics)
BSA (m²) = 0.024265 × height(cm)0.3964 × weight(kg)0.5378
Developed using a wide range of body sizes, including infants and children, and frequently used in pediatric practice.
4. Boyd
BSA (m²) = 0.0003207 × height(cm)0.3 × weight(kg + 0.0001)0.7285 − 0.0188 × log10(weight(kg))
5. Gehan & George
BSA (m²) = 0.0235 × height(cm)0.42246 × weight(kg)0.51456
How the calculator works
- Convert units (if needed) so height is in cm and weight in kg.
- Compute BSA using the selected formula.
-
Optionally apply a BSA cap (e.g., 2.0 m²) if
your protocol limits BSA for dosing:
Effective BSA = min(calculated BSA, BSA cap)
-
Multiply effective BSA by the dose per m²:
Uncapped dose (mg) = Effective BSA × dose (mg/m²)
-
Optionally apply a maximum total dose:
Capped dose (mg) = min(uncapped dose, max dose)
-
Finally, apply rounding to match vial sizes
or policy:
Rounded dose = round(capped dose ÷ step) × step
Clinical considerations and limitations
- Obesity and underweight: For very high or very low BMI, some protocols recommend using adjusted or ideal body weight, or capping BSA. Always follow your local guidelines.
- Renal and hepatic function: Many drugs require dose adjustment based on kidney or liver function in addition to BSA.
- Rounding: Rounding rules vary by institution and drug. This tool offers flexible rounding, but you must ensure it matches your practice.
- Verification: High-risk medications (e.g., chemotherapy) should always be double-checked by another clinician and/or pharmacy system.
Frequently asked questions
Is there a single “best” BSA formula?
No single formula is universally superior. Differences between formulas are usually small (often <3–5%) for typical adult sizes. Mosteller is widely accepted for its simplicity; Haycock is often preferred in pediatrics. Use the formula recommended by your institution or the drug label.
Why do some protocols cap BSA at 2.0 m²?
In very large adults, BSA can increase faster than drug clearance, potentially leading to overdosing if BSA-based dosing is used without limits. Many oncology protocols therefore cap BSA at 2.0 m² (or another value) to avoid excessively high doses. This calculator allows you to set such a cap explicitly.
Can I use this calculator for veterinary BSA dosing?
This tool is designed for human dosing and uses human BSA formulas. Veterinary BSA formulas and dosing regimens differ by species. For animals, use species-specific calculators and follow veterinary guidelines.
Is my data stored?
Calculations and dosing history are kept only in your browser session to help you compare regimens. They are not persisted to a server or linked to identifiable patient information.