How Much Sunscreen Do I Really Need? Here's A Guide

Sunscreen is crucial for keeping your skin healthy and glowing in the summer sun.

Experts recommend anyone older than 6 months to use sunscreen daily to prevent skin damage from long-term sun exposure.

However, the amount of sunscreen a person needs depends on a variety of factors including sun intensity and skin type. Here’s how to gauge how much sunscreen you’ll need this summer season:

What Is SPF?

SPF stands for sun protection factor and is a measure of how well your sunscreen protects your skin from ultraviolet (UV) rays. There are two types of UV rays: UVA rays, which can cause premature aging, and UVB rays, which are the primary cause of sunburns.

Sunscreen with a higher SPF blocks a larger percentage of harmful UV rays from reaching your skin. According to the MD Anderson Cancer Center, an SPF 15 sunscreen blocks 93% of UVB radiation while an SPF 30 sunscreen blocks 97% of radiation.

How Much Sunscreen Do I Need?

Use broad-spectrum protection sunscreen with water resistance and an SPF of 30 or higher, the American Academy of Dermatology (AAD) recommends. Most adults should apply 1 ounce of sunscreen, or about one shot glass full, to cover all exposed parts of their body.

The amount of sunscreen you need also depends on a person’s skin type, the amount of sunscreen you apply and how often you apply the sunscreen. For example, fair-skinned individuals absorb more solar energy than darker-skinned individuals and should reapply more often.

In addition to wearing sunscreen, other dermatologist recommendations include seeking shade when appropriate, dressing to protect yourself from the sun and avoiding tanning beds.

(MORE: Swimming? Sweating? Here's How Fast Your Sunscreen Wears Off)

How Often Should I Reapply?

As a general rule, Johns Hopkins Medicine recommends reapplying sunscreen every two hours. However, this interval also depends on both the sun’s intensity and what you’re doing.

Outdoor activities during midday will expose you to more solar energy than being outside in the mornings and evenings. If you’re sweating or swimming, you may want to reapply sunscreen more frequently. If you are working indoors or away from windows, you may not need to reapply at all.