Full skin surface
—grams
— teaspoons per application
Free evidence-based tool
How much sunscreen do you actually need?
Sunscreen earns its labeled SPF at a specific thickness: 2 mg per cm² of skin. Enter three measurements and I’ll turn that into a body-part-by-body-part dose map.
8 body regions 2 useful units 1 less sunscreen mystery
Built from the Schlich body-surface-area formula and the FDA sunscreen testing dose.
Personal dose map
Calculate yours
Your result
Your sunscreen dose map
Your detailed plan is ready.
Common exposed areas
—grams
— teaspoons across the regions below
Estimated BSA
—m²
Estimated from your height, weight, and formula selection
Front
Back
Labels show grams per application. The map is illustrative, not anatomically exact.
| Body area | Area | Grams | Teaspoons |
|---|
About 12.5% is not itemized: soles, hair-covered skin, and areas normally covered by swimwear. Use the full-body total if those areas are exposed.
The short version
Your SPF number assumes enough sunscreen.
In the FDA SPF test, sunscreen is spread evenly at 2 mg/cm². This calculator estimates your body surface area, assigns published percentages to each region, and converts the resulting mass into grams and kitchen teaspoons.
body area×region %×2 mg/cm²=your dose
Teaspoons are convenient but less precise because sunscreen density and measuring technique vary. A small gram scale is the better reality check.
Use the number well
Coverage is a practice, not a one-time measurement.
Apply before exposure
Spread it generously and evenly about 15 minutes before going outside.
Mind the missed spots
Ears, hairline, neck, hands, and tops of feet are easy to under-apply or skip.
Reapply by the label
At least every two hours, and after swimming, sweating, or towel drying as directed.
Use more than sunscreen
Clothing, shade, hats, and sunglasses add protection without adding another teaspoon.
Questions, answered
What the calculator can—and can’t—tell you.
Why does the amount of sunscreen matter?
Labeled SPF is tested with sunscreen applied at 2 milligrams per square centimeter of skin. A thinner, uneven layer can provide substantially less protection than the number on the bottle suggests.
What does this calculator include?
It estimates body surface area from height, weight, and the sex-specific Schlich formula, then calculates a 2 mg/cm² dose for each body region. Real bodies and product densities vary, so treat the result as a practical estimate.
Why does the formula ask for sex?
The published Schlich formula uses different coefficients for female and male body-shape datasets. Choose the dataset that best matches your body composition. This field is used only for the calculation.
Do I need to apply this much every day?
Apply sunscreen to skin that will be exposed. Clothing, shade, hats, and sunglasses can reduce the area that needs sunscreen. Follow the directions and reapplication timing on your product label.
Primary references
Show me the receipts.
- FDA sunscreen labeling and SPF effectiveness testing guidance
- Application of sunscreen: theory and reality
- Calculation of sunscreen application thickness
- Schlich body-surface-area formula
This educational calculator is not medical advice and does not replace product directions or guidance from a qualified clinician. Body proportions and sunscreen formulations vary.