Body Surface Area Calculator
Calculate your body surface area using four validated formulas — DuBois, Mosteller, Haycock, and Boyd. Understand how BSA is used in chemotherapy dosing, burn care, and clinical medicine.
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Enter your values above to see the results.
Tips & Notes
- ✓Mosteller is the simplest formula and is widely used in oncology practice. DuBois is historically the most cited but was derived from only 9 subjects and is less accurate at weight extremes.
- ✓Normal BSA for adult women averages 1.6–1.7 m²; for adult men, 1.9–2.0 m². Values outside 1.2–2.6 m² are uncommon and may prompt clinical review of the measurements.
- ✓BSA changes more slowly than weight — a 10% change in body weight produces roughly a 5% change in BSA. This stability is why it is preferred for dosing over direct weight-based calculations.
- ✓For pediatric patients, Haycock is the most validated formula and should be preferred over DuBois or Mosteller in children.
- ✓BSA-based chemotherapy dosing uses 1.73 m² as the "standard" adult BSA. Your actual BSA divided by 1.73 gives your scaling factor relative to that reference.
Common Mistakes
- ✗Using adult formulas (DuBois, Mosteller) for young children, where Haycock is significantly more accurate.
- ✗Assuming that the different formulas will give the same result — they typically agree within 5–10%, but that can translate to meaningful dose differences for narrow-window drugs.
- ✗Using BSA for fitness or weight-management purposes, where it has no direct relevance — BSA is a clinical measurement, not a body composition metric.
- ✗Forgetting that BSA-based chemotherapy doses are still approximations — pharmacokinetic monitoring (measuring actual drug blood levels) is more precise where available.
- ✗Entering height in meters instead of centimeters in the formula — the Mosteller formula specifically requires centimeters, not meters.
Body Surface Area Calculator Overview
Body surface area is the sizing system for some of medicine's most powerful and toxic treatments. Getting it right is the difference between an effective dose and a dangerous one.
Mosteller and DuBois formulas — adult use:
Mosteller Formula (simplest, widely used in oncology): BSA (m²) = √[(height cm × weight kg) ÷ 3600] DuBois & DuBois Formula (historically most cited): BSA (m²) = 0.007184 × height^0.725 × weight^0.425
EX: Patient: 172 cm tall, 74 kg Mosteller: √[(172 × 74) ÷ 3600] = √[12,728 ÷ 3600] = √3.536 = 1.88 m² DuBois: 0.007184 × 172^0.725 × 74^0.425 = 0.007184 × 45.37 × 8.61 = 0.007184 × 390.6 = 1.81 m² For a drug dosed at 60 mg/m²: Mosteller dose = 113 mg, DuBois dose = 109 mg
Haycock and Boyd formulas — pediatric and specialized use:
Haycock Formula (most accurate for children): BSA (m²) = 0.024265 × height^0.3964 × weight^0.5378 Boyd Formula (accounts for weight curvature): BSA (m²) = 0.0003207 × height^0.3 × weight^(0.7285 − 0.0188 × log₁₀(weight))
EX: Child: 120 cm tall, 22 kg Haycock: 0.024265 × 120^0.3964 × 22^0.5378 = 0.024265 × 10.61 × 4.86 = 1.25 m² Adult drug dose of 100 mg/m² → pediatric dose = 100 × 1.25 = 125 mg Compare: adult at 1.85 m² → 185 mg (32% more per dose)
BSA formula comparison — history and best use case:
| Formula | Year | Best used for | Known limitation |
|---|---|---|---|
| DuBois & DuBois | 1916 | Historical reference, adult oncology | Based on 9 subjects; less accurate at extremes |
| Mosteller | 1987 | Clinical oncology, simplest calculation | Slightly overestimates in obese patients |
| Haycock | 1978 | Pediatric patients (most validated) | Performs worse in very obese adults |
| Boyd | 1935 | Wide weight range including obesity | Complex formula; rarely used clinically today |
Reference BSA values and clinical drug dosing context:
| BSA application | How BSA is used | Clinical example |
|---|---|---|
| Chemotherapy dosing | Drug dose (mg) = dose rate (mg/m²) × BSA | Doxorubicin 60 mg/m² × 1.85 m² = 111 mg |
| Burn severity (Rule of Nines) | % BSA burned guides fluid resuscitation | 30% BSA burns → 4 mL/kg/% burn in first 24h |
| Cardiac index | CI = cardiac output ÷ BSA | 5.0 L/min ÷ 1.85 m² = 2.70 L/min/m² |
| Pediatric drug dosing | Child dose = adult dose × (child BSA ÷ 1.73 m²) | 1.25 m² ÷ 1.73 × adult dose = 72% of adult dose |
| Renal function (GFR normalization) | GFR adjusted to 1.73 m² standard body surface | Raw GFR 85 mL/min normalized to BSA |
BSA-based dosing has been the standard for chemotherapy since the 1950s, but it is not without controversy. Some oncologists argue that BSA correlates poorly with drug clearance for certain agents, and that pharmacokinetic-guided dosing (adjusting based on measured drug levels in blood) would be more precise. For now, BSA remains the practical standard in most oncology settings because it is accessible, reproducible, and has decades of dosing data behind it. For anyone receiving chemotherapy, understanding your BSA means understanding why your dose is what it is — and being able to have an informed conversation with your oncologist if questions arise.
Frequently Asked Questions
Normal BSA ranges from approximately 1.5–1.8 m² for adult women and 1.8–2.1 m² for adult men, depending on height and weight. The commonly cited "standard" in clinical dosing is 1.73 m², which represents a median adult value. A petite woman (155 cm, 55 kg) might have a BSA of 1.55 m², while a tall man (190 cm, 95 kg) might have 2.25 m². These differences are clinically significant for drug dosing and explain why weight-based dosing alone can be inaccurate.
BSA was adopted for chemotherapy dosing in the 1950s because early research suggested it correlated better with drug metabolism and toxicity than total body weight alone. The reasoning was that metabolic processes (including drug clearance by the liver and kidneys) scale more proportionally with body surface than with mass. While this assumption has been challenged by more recent pharmacokinetic research, BSA-based dosing remains standard because it is simple, reproducible, and backed by decades of clinical data establishing safe dose ranges.
In obese patients, BSA calculated from actual body weight can produce doses so high they risk severe toxicity. Many oncology centers use a capped or adjusted BSA for patients with BMI above 30, typically limiting the calculation weight to a value between ideal body weight and actual weight. This is an active area of clinical debate — underdosing in obesity can reduce treatment efficacy, while full-weight dosing increases toxicity. The American Society of Clinical Oncology generally recommends using actual body weight for most chemotherapy agents unless specific toxicity concerns exist.
Yes — they measure completely different things. BMI (Body Mass Index) is a ratio of weight to height squared that categorizes weight status relative to height. It has no physical units and is used as a screening tool for health risk. BSA (Body Surface Area) is an actual physical measurement — the total area of your body's external surface in square meters. BSA incorporates both height and weight but produces an area measurement, not a ratio. BSA is primarily used in clinical contexts (drug dosing, cardiac measurements), while BMI is used for population-level health screening.
You can calculate your BSA, but applying it to calculate your own chemotherapy dose is not advisable without your oncologist's involvement. Chemotherapy dosing involves not just BSA but also kidney function (which affects drug clearance), prior treatment history, current blood counts, specific drug protocol, and individual tolerance factors. The oncologist uses BSA as one input in a complex dosing calculation that has been refined through clinical trials. If you want to understand your dose, discussing the mg/m² rate and your BSA calculation with your oncologist is the right approach.
The Rule of Nines divides the body surface into regions each representing approximately 9% (or 18% for larger areas) of total BSA: the head and neck account for 9%, each arm 9%, the anterior trunk 18%, the posterior trunk 18%, each leg 18%, and the perineum 1%. This allows emergency clinicians to rapidly estimate what percentage of BSA is burned, which determines fluid resuscitation volumes using the Parkland formula: 4 mL × body weight (kg) × percentage BSA burned, given over 24 hours. Knowing your actual BSA can refine these estimates beyond the rule-of-nines approximation.