Body Surface Area Calculator

Calculate body surface area (BSA) using the Du Bois and Mosteller formulas. Free, instant, no signup.

Formula: Du Bois: BSA = 0.007184 × weight(kg)^0.425 × height(cm)^0.725

How to use the Body Surface Area Calculator

  1. Enter your values. Fill in the fields with your numbers.
  2. Calculate. Press Calculate to run the body surface area calculator.
  3. Use the result. Copy the result or try a related tool next.

Why use our Body Surface Area Calculator

Instant results. Enter your figures and the body surface area calculator returns an answer in seconds.
Free & private. Runs in your browser — no signup, and nothing is sent to a server.
Accurate. Uses standard formulas so you can rely on the numbers.

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About the Body Surface Area Calculator

The Body Surface Area Calculator estimates the total external area of your body in square metres (m2) from two simple measurements: your height and your weight. Body surface area, or BSA, is widely treated as a better proxy for metabolic mass than weight alone because it tracks more closely with organ size, blood volume, and how the body processes substances. Clinicians lean on it for tasks like scaling medication doses, indexing cardiac output to body size, and reporting kidney filtration rates. This tool turns the standard published equations into an instant result so you can check a figure without doing the exponents by hand.

Reach for this calculator any time a number needs to be related to body size rather than weight. The most familiar use is chemotherapy and other cytotoxic drug dosing, where doses are commonly expressed in milligrams per square metre and multiplied by the patient's BSA. It is also used to compute the cardiac index (cardiac output divided by BSA, normal range roughly 2.5 to 4.0 L/min/m2) and to normalise estimated glomerular filtration rate to the standard 1.73 m2 reference body. Students, nurses, and caregivers also use it simply to double-check a value that appears on a chart or in a textbook problem.

Under the hood, the tool applies one of the long-established BSA formulas. The Mosteller formula is the simplest and most popular: BSA = the square root of (height in cm multiplied by weight in kg, divided by 3600). The older Du Bois and Du Bois formula (1916) uses exponents: BSA = 0.007184 x height(cm)^0.725 x weight(kg)^0.425. Other published variants such as Haycock and Gehan-George exist and give very similar answers for typical adults. For reference, average adult BSA is roughly 1.9 m2 for men and 1.6 m2 for women, while a newborn sits near 0.25 m2.

All of the maths runs entirely in your browser, so the height and weight you enter are never uploaded, stored, or shared. On accuracy: BSA is an estimate derived from formulas fitted to limited historical samples, so different equations can differ by a few percent, and the result is most reliable for people of average body composition. It is a useful planning and learning figure, not a clinical decision in itself. Any real medication dose, cardiac, or kidney assessment should be confirmed by a qualified healthcare professional using validated tools and the patient's full clinical picture.

Frequently asked questions

Which BSA formula does this calculator use?

It is built around the Mosteller formula, BSA = square root of ((height in cm x weight in kg) / 3600), which is the most widely used method because it is simple and accurate for both adults and children. The older Du Bois formula gives nearly identical results for typical body sizes.

What is a normal body surface area?

There is no single normal value because BSA scales with size, but the average adult is roughly 1.9 m2 for men and 1.6 m2 for women. A newborn is about 0.25 m2 and a five-year-old child around 0.75 to 0.8 m2.

Why is BSA used to calculate medication doses?

BSA correlates better than body weight with metabolic rate, blood volume, and organ function, so it gives a more consistent estimate of how a drug will be distributed. Many chemotherapy and cytotoxic agents are therefore prescribed in milligrams per square metre multiplied by the patient's BSA.

Do the different BSA formulas give different answers?

They agree closely for average adults, typically within a few percent of each other. Larger differences can appear at the extremes of height and weight, which is one reason BSA is treated as an estimate rather than an exact measurement.

Should I enter height and weight in metric or imperial units?

The standard formulas use centimetres and kilograms, and BSA is reported in square metres. If you only know your measurements in feet, inches, and pounds, convert them first or use the unit options provided so the result stays accurate.

From our blog

Salary to Hourly: How to Find What Your Time Is Really Worth

By the Super Simple Digital Tools Team · Updated June 2026

A salary hides one important fact: how much you are paid for each hour you actually work. Two people earning $60,000 can have very different deals. One works a steady 40 hours a week and earns about $28.85 an hour; the other routinely puts in 55-hour weeks and is really making closer to $20.98 for the same paycheck. Converting salary to hourly strips away the headline number and shows the rate your time commands, which is the figure that matters when you negotiate, job-hunt, or decide whether a promotion is worth the extra hours.

The core calculation is short. Take your annual salary, then divide it by your hours per week multiplied by your weeks per year. The familiar 2,080-hour benchmark assumes 40 hours across all 52 weeks, but the second number is where most people get it wrong. If you take two weeks of unpaid leave, you work roughly 50 weeks, not 52, so your effective rate is higher than the simple 2,080 division suggests. Adjust the weeks figure to match how much of the year you are genuinely on the clock and the result becomes far more honest.

Schedule length is the other lever. Salaried roles often expect more than 40 hours without extra pay, and every additional hour quietly lowers your real rate. Run the numbers both ways before accepting an offer: calculate the hourly rate at the official 40 hours, then again at the hours the role actually demands. The gap between those two figures is the unpaid premium you would be giving up. For hourly and overtime-eligible roles the reverse is true, since hours beyond 40 can earn time-and-a-half, which a flat salary never does.

Keep in mind that the converted rate is gross. Federal and state income tax, the 6.2% Social Security and 1.45% Medicare FICA contributions, health premiums, and any retirement deductions all come out before money reaches your account, so your net hourly take-home is lower than the calculator shows. On the other side of the ledger, benefits like employer retirement matching, paid holidays, and insurance can add meaningful value that a raw hourly number does not capture. Treat the gross rate as a clean comparison baseline, then layer taxes and benefits on top.

Used this way, salary-to-hourly conversion becomes a decision tool rather than a curiosity. Compare a staff job against a contract gig by putting both on the same hourly footing. Check whether a 10% raise that comes with a heavier workload actually beats your current rate per hour. Price freelance work so it clears your old employed wage after you account for unpaid admin time. The arithmetic takes seconds, but the perspective it gives on your real earning power lasts well beyond a single calculation.

  • Use the real hours you work, not the contracted 40, so an offer that expects long weeks shows its true lower hourly rate.
  • Lower the weeks-per-year figure below 52 to reflect any unpaid time off, which raises your effective rate.
  • Remember the result is gross; estimate roughly 20-35% off for income tax and the 7.65% FICA total to gauge take-home.
  • When comparing offers, add the value of benefits and overtime separately, since the hourly number alone leaves them out.

Read the full guide →

Tool by the Super Simple Digital Tools Team. Reviewed by our editorial team. Free to use, no signup required.

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