[Routine Help] how often does sunscreen need to be applied?

Beauty Tips For Body Care
If u have an spf 50 how often do u apply on a sunny day outside? How often do u apply indoors or outdoors in miserable british weather?Does frequency of application change if i only use Spf30?Also how much sunscreen does dr dray apply and im wondering if I really need that much sunscreen?
Girls Blog 2015
Submitted by lamyH