Sunscreen Calculator: How Much Sunscreen Do You Need?

How Much Sunscreen Should You Apply?

Most people apply far too little sunscreen. Dermatologists recommend 2 mg per square centimeter of skin, which translates to roughly 1 ounce (30 ml) for full body coverage. Our calculator breaks this down by body area so you know exactly how much to use on each part.

The "teaspoon rule" is an easy way to remember: half a teaspoon for the face, one teaspoon per arm, two teaspoons per leg, and two teaspoons each for the front and back of the torso.

Why the Right Amount Matters

Studies show that most people apply only 25-50% of the recommended amount of sunscreen. When you apply half the recommended amount of SPF 30, you actually get protection equivalent to only about SPF 5-7. Proper application is just as important as the SPF number on the bottle.

Frequently Asked Questions

How often should I reapply sunscreen?

Every 2 hours when outdoors, regardless of SPF level. Reapply immediately after swimming, heavy sweating, or towel-drying. No sunscreen is truly waterproof — "water-resistant" formulas last 40-80 minutes in water.

Does a higher SPF mean I need less sunscreen?

No. The amount of sunscreen needed is the same regardless of SPF. Higher SPF provides more UV filtration per unit applied, but only when you apply the full recommended amount. Using less defeats the purpose of higher SPF.

Should I use sunscreen on cloudy days?

Yes. Up to 80% of UV rays penetrate clouds. If the UV index is 3 or higher (which it often is even on overcast days), you should apply sunscreen to exposed skin.