SUNSTOKE

Sunscreen Amount Calculator

Tick the areas you’re covering and see how much sunscreen one coat takes at the density SPF is tested at, in grams, fluid ounces, teaspoons and shot glasses, per coat and for the day.

Which areas are you covering?
Average adult about 1.8 m² (0.2 to 3.0 accepted). A whole body never gets less than the FDA's one ounce.
The FDA: reapply at least every two hours, and more often if you're sweating or swimming. Count each coat.

How much to use

Per application
35.7 g
In fluid ounces
1.21 fl oz
In teaspoons
7.2 tsp
In "shot glasses" (30 mL)
1.19
Skin area covered
17,820 cm²
Total for 2 coats
71.4 g
  • FDA: "An average-sized adult or child needs at least one ounce of sunscreen (about the amount it takes to fill a shot glass) to evenly cover the body from head to toe."
  • FDA: "Reapply sunscreen at least every two hours, and more often if you're sweating or swimming."
  • American Academy of Dermatology: "People who get sunburned usually didn't reapply, used too little sunscreen, or used an expired sunscreen."
  • FDA: "Sunscreen is not recommended for infants under six months old."

Based on the 2 mg/cm² density SPF is tested at (21 CFR 201.327), every amount rounded up. Lotion is taken as about 1 g per mL.

The amount is the part everyone skips

The SPF on a bottle was measured with two milligrams of sunscreen on every square centimeter of skin. For a whole adult body that is more than a shot glass a coat, and the FDA’s minimum is one ounce. Seeing it in teaspoons and ounces makes it concrete.

Cover up first and the amount drops: the American Academy of Dermatology says to apply sunscreen to all skin not covered by clothing, and WHO puts shade and clothing ahead of sunscreen. Untick the areas a shirt, hat or trousers will cover.

Frequently Asked Questions

Where does the 2 mg/cm² figure come from?

It is the density SPF is tested at. The FDA's test method (21 CFR 201.327) says: "Apply the sunscreen test product and the SPF standard at 2 milligrams per square centimeter (mg/cm2) to their respective test sites." The SPF on the label was measured at that amount.

How much is that for a whole body?

For an average adult (1.8 m²) it works out to about 35.7 g a coat. The FDA's own figure is a floor this calculator never goes below: "An average-sized adult or child needs at least one ounce of sunscreen (about the amount it takes to fill a shot glass) to evenly cover the body from head to toe."

Why does using too little matter?

The American Academy of Dermatology: "People who get sunburned usually didn't reapply, used too little sunscreen, or used an expired sunscreen."

Is the body-area estimate exact?

No. It uses the rule of nines, a burn-care convention for splitting an adult body into rough shares, applied to the body surface you enter. Every amount is rounded up, and a whole body never gets less than one ounce.

What about babies?

The FDA: "Sunscreen is not recommended for infants under six months old." and "Ask a doctor before applying sunscreen to children under six months of age."

General information, not medical advice. Follow your product’s label. The words in quotation marks are the FDA’s and the AAD’s, checked on their sites on October 6, 2026.