Two numbers appear on every Asian sunscreen, and they measure different things.
SPF: the burning one
SPF measures protection against UVB — the rays that burn. SPF 30 filters roughly 97% of UVB, SPF 50 around 98%. The jump from 30 to 50 is smaller than the numbers suggest, and neither is a full block.
PA: the ageing one
PA measures protection against UVA — the rays that penetrate deeper and drive pigmentation and long-term ageing. UVA passes through cloud and window glass, which is why dermatologists recommend sunscreen indoors near windows too.
PA+ — some protection
PA++ — moderate
PA+++ — high
PA++++ — very high
In Indian sun, PA+++ or higher is the sensible floor.
How much to use
The lab rating assumes about two finger-lengths of product for the face and neck — far more than most people apply. Half the amount does not give half the protection; it gives considerably less. Reapply every two to three hours outdoors.
Why Asian sunscreens are popular
They tend to have lighter textures and less white cast than older Western formulations, which makes daily use realistic. The best sunscreen is the one you will actually put on every morning.