Free calculator
Sunscreen Amount Calculator
SPF labels assume 2 mg of sunscreen per square centimetre of skin. Most people use a quarter to half of that, so they get a fraction of the protection printed on the bottle.
How it works
Body surface area uses the Mosteller formula: √(height in cm × weight in kg ÷ 3600). The exposed share is estimated from the rule of nines for your clothing choice, then multiplied by 2 mg per cm². One gram is treated as about one millilitre, and a teaspoon as 5 ml.
Reapply every two hours outdoors, and straight after swimming, heavy sweating or towel drying.
Frequently asked questions
What SPF should I use in India?
SPF 30 to 50 with PA+++ or higher, applied generously, protects well for daily use. Higher SPF does not replace reapplication.
Do I need to reapply over makeup?
If you are outdoors, yes. A sunscreen stick, spray or SPF powder is easier than rubbing cream over makeup.
Is the “two finger” rule accurate?
Two strips of sunscreen along your index and middle fingers (about 1.2 ml) is a good guide for face and neck.
General estimates for information only. Not medical or professional advice. Nothing you enter is saved or sent to us.
