Sunscreen Amount Calculator
Full Body Application
Calculate sunscreen needed for your body based on areas exposed
hours
Face & Neck Only
Quick calculation for daily facial sunscreen
Formula
Sunscreen amount = Body surface area (cm²) × 2 mg/cm² | Face ≈ 1.2 ml (~1/4 tsp) | Full body ≈ 30 ml (~1 oz) | Reapply every 2 hours
Frequently Asked Questions
How much sunscreen should I apply to my face?
Apply about 1/4 teaspoon (1.2 ml) to your face, or two finger-length strips of product. Most people under-apply by 50-75%, which significantly reduces protection.
How often should I reapply sunscreen?
Reapply every 2 hours when outdoors, and immediately after swimming, sweating, or towel-drying. Even water-resistant sunscreen should be reapplied after 40-80 minutes of water activity.
What is the difference between SPF 30 and SPF 50?
SPF 30 blocks about 96.7% of UVB rays, while SPF 50 blocks about 98%. The difference is small but meaningful. SPF 15 blocks ~93.3%. No sunscreen blocks 100% of UV rays.
Does higher SPF mean I can stay out longer?
Technically yes, but dermatologists recommend reapplying every 2 hours regardless of SPF level. Higher SPF provides better protection at the same application thickness, especially since most people under-apply.
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