Beauty & Skincare
Sunscreen Amount & Reapply Calculator
Work out how much sunscreen you need, when to reapply it, and how many days a bottle lasts.
About the Sunscreen Amount & Reapply Calculator
SPF ratings are tested at 2 mg of sunscreen per cm² of skin. Most people apply far less, so they get much lower protection than the number on the bottle.
Reapply every 2 hours outdoors, and straight after swimming, heavy sweating or towelling off. Shade and clothing help too.
Frequently asked questions
Do I need sunscreen indoors or when it is cloudy?
UVA passes through clouds and window glass, so daily sunscreen on exposed skin is recommended, especially near windows.
What SPF should I use?
Dermatologists commonly recommend broad-spectrum SPF 30 or higher, applied generously.