How much SPF is better to wear sunscreen in summer?

In summer, just wear sunscreen with SPF30 or so.

SPF value refers to the abbreviation of Sun Protection Factor, which represents the degree of UVB protection of a product. It is based on the occurrence of sunburn erythema on the skin after using or not using sunscreen products (i.e. MED index) : MiniErythema Dose is determined based on the minimum time (the lowest redness-causing dose for the skin), which varies among people with different skin types.

For Asians, the skin will generally become red after being exposed to the sun for 15 minutes. SPF20 means that using this product can block ultraviolet rays for 15 minutes × 20 times = 300 minutes. For example, if you are sunburned in 15 minutes without any protection, if you apply an SPF20 sunscreen product, you will not be sunburned until 300 minutes (i.e. 5 hours).

General first-level protection--below SPF15: the most basic sun protection. Applicable occasions: any cloudy day, or indoors where the skin is damaged by various light sources. Choose a product: Most day creams contain this level of sun protection, and some eye creams and lipsticks also contain it.

Second level protection--SPF15-20: medium sun protection. Applicable occasions: outdoors in sunny weather in autumn and winter, or indoors in cloudy weather in summer. Choose products: sunscreen day cream, sunscreen primer, sunscreen powder, and foundation.

Level 3 protection--SPF20-30: high sun protection. Applicable occasions: Outdoors on sunny days in summer, or seats near windows indoors in summer. Choose products: sunscreen day cream, sunscreen primer, sunscreen powder, and foundation.

Fourth level of protection--SPF30 or above: ultra-high sun protection. Applicable occasions: outdoor activities under particularly strong sunlight, such as beaches, mountain climbing, etc. Choose products: sunscreen day cream, sunscreen cream.