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¼ tsp ≈ 1.25ml (derm-recommended for face)
Morning + midday reapply = 2
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How we calculated this
SPF testing uses 2mg/cm² of product, which translates to ~1.25ml per face-and-neck application. If you're using less than that, your actual SPF protection drops exponentially (SPF 30 applied at half the amount gives you roughly SPF 5-8).
This calculator assumes two applications per day by default, morning + midday reapply. For face-only, we use 1.25ml per application; for face + body, we multiply by 7 to approximate full-body coverage.
Frequently asked
How much sunscreen should I use on my face? +
Dermatologists recommend ¼ teaspoon (about 1.25ml) for the face and neck, roughly two finger-lengths of product. Most people use half that.
How long should a bottle of face sunscreen last? +
Applied correctly, a 1.7 fl oz (50ml) bottle should last 30-40 days. If yours lasts 3+ months, you're likely under-applying.
Is it cheaper to use body sunscreen on your face? +
Usually yes per ounce, but body formulas are often heavier, whiter, and less pleasant on the face, leading to skipping. Compliance matters more than cost.
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