How Much SPF : Science Behind Choosing The Right Sunscreen SPF For Face

Our body needs sunlight for vitamin D but overexposure to sunlight can be dangerous. As per a research by, exposure to the sun’s ultraviolet (UV) rays can cause skin damage, premature aging, or skin cancer.

UV rays can be divided into three types – UVA, UVB, and UVC based on different wavelength.

How UV rays effect your skin

#1. UVA 

UVA rays have a longer wavelength between 320 and 400 nm that can penetrate into the deeper layers of the skin (the dermis). UVA can cause premature skin aging, wrinkles, sagging, or skin cancer.

UVA rays account for 95% of the UV radiation reaching the Earth’s surface.

#2. UVB 

Medium wavelength between 290 and 320 nm UVB radiation makes up the remaining 5% of the UV radiation reaching the Earth. UVB rays are absorbed by the epidermis outer layer of skin, and also responsible for the production of vitamin D in our bodies. Vitamin D strengthens your teeth and bones by regulating the calcium level in our body. 

Overexposure to the sun’s UVB rays may cause sunburn, skin cancer, cataracts and makes skin darker by increasing melanin production. However, people with darker skin generally produce less vitamin D due to the high concentration of melanin (darker pigment) in the skin. 

People with lighter skin can make enough vitamin D in 10 to 15 minutes of sun exposure at least three times a week. Whereas darker skinned people need 10 times more sunlight to produce the same amount of vitamin D.

#3. UVC

The most harmful UV radiation is the shortest wavelength UVC between 100 and 290 nm. However, this radiation never reaches the earth’s surface because the ozone layer completely absorbs it.  

Sunscreen is one of the easiest solutions to prevent the sun’s UV rays to penetrate skin.

Choosing the right SPF sunscreen for your skin can be confusing. Here’s a guide on how sunscreen works and how to choose the right SPF sunscreen for your skin.

How Does Sunscreen Work

Sunscreen is a filter that blocks the sun’s UV rays from reaching your skin. It works by absorbing or reflecting the sun’s energy that strikes the skin, preventing burns and long-term skin damage.

How Does Sunscreen Work

#1. Physical / Mineral Sunscreen 

Physical or mineral sunscreen contains titanium dioxide and zinc oxide. Physical sunscreen works to deflect and scatter the UV rays before they penetrate your skin. Physical sunscreens are non-comedogenic, which means they do not clog the pores.

Mineral-based sunscreen does not irritate the skin, so it becomes the best option if you have sensitive or acne-prone skin.

#2. Chemical Sunscreen 

Chemical sunscreen is made with oxybenzone, avobenzone, octinoxate, and octisalate that absorb UV rays and turn them into heat. Then this heat is released from the skin. You can apply the chemical sunscreen under the makeup and spread it easily on your skin. 

The downside to using chemical sunscreen is that it contains chemical ingredients that may irritate a sensitive skin

3 Things To Consider When Choosing The Right SPF Sunscreen

Regular use of sunscreen with SPF 15 or higher broad-spectrum reduces the risk of developing skin cancer – squamous cell carcinoma by about 40%, melanoma by 50% and premature skin aging by 24%.

#1. SPF

Sun Protection Factor or SPF, is a measure of how well and for how long a sunscreen protects your skin from UVB radiation. A Higher SPF number provides more protection against harmful sun UVB rays.

For example – If your unprotected skin will burn in 10 minutes, SPF 30 will protect your skin 30 times longer = 300 (10X30) minutes. 

Different levels of SPF

How much SPF sunscreen for face

1. SPF 15 – Sunscreen with SPF 15 blocks about 93% of UVB rays. This means if you go outside without sunscreen then 100% photons of radiation penetrate into your skin. 

A rating of SPF 15 means that 93% of photons are blocked from being absorbed. Only 7% of photons can enter your skin. SPF 15 is ideal for people who have occasional exposure, like walking your dog or driving to work

2. SPF 30 sunscreen for face – SPF 30 gives you 97% protection against UVB rays; only 3% of photons would be able to penetrate your skin. SPF 30 is good for outdoor activities such as running, hiking, and outdoor sports. Most dermatologists recommend SPF 30 or higher.

3. SPF 50 sunscreen for face – SPF 50 sunscreen gives you better protection to your skin by filtering 98% of UVB rays. Only 2% of photons penetrate your skin. SPF 50 sunscreen only gives you 1% more protection over SPF 30. You can choose either SPF 30 or 50 according to your sun exposure because no sunscreens offer 100% protection from UVB rays.

PA rating in sunscreen 

Some sunscreen comes with PA+ (Protection Grade of UVA). This is a rating system developed in Japan to represent how effectively a sunscreen protects against UVA rays. Sunscreen with different PA ratings provides different levels of UVA protection such as –

  • Sunscreen with a PA rating of PA+ provides some UVA protection.
  • PA++ offers moderate UVA protection.
  • PA+++ provides high UVA protection.
  • PA++++ provides extremely high UVA protection.

#2. Broad Spectrum 

Sunscreen labeled with a broad spectrum protects your skin from both UVA and UVB rays. This type of sunscreen is ideal for people who are concerned about the long-term effects of sun exposure. It also helps reduce the risk of skin cancer.

#3. Water Resistant Sunscreen 

Water-resistant sunscreen is most effective for swimming or sweating. This sunscreen is labeled with 40 or 80 minutes, which indicates how long the sunscreen remains effective in the water and sweat. You should reapply sunscreen every 80 minutes for maximum protection.

Sunscreen According To Your Skin Type

#1. Sunscreen For Dry Skin

If you have dry skin, you should use sunscreen that has hydrating ingredients, such as hyaluronic acid, glycerin, and ceramides. These ingredients help to keep your skin hydrated and prevent dryness and irritation. If you want to use makeup then first use sunscreen moisturizer, second setting powder for dry skin and then finally use makeup.

Best sunscreen for dry skinNeutrogena Ultra sheer Sunscreen, SPF 55    

#2. Sunscreen For Oily Skin

People with oily skin use water-based sunscreens and look for a mattifying formula that will absorb excess oil throughout the day. 

Best mineral sunscreen for oily skinCeraVe Tinted Sunscreen with SPF 30

#3. Sunscreen For Sensitive Or Acne Prone Skin 

Look for a sunscreen that contains mineral ingredients if your skin is sensitive and prone to irritation. Avoid products that contain alcohol, preservatives, fragrances, and oxybenzone because that may cause irritation to sensitive skin.

Best pick for sensitive skin EltaMD UV Daily SPF 40 Sunscreen

Best Acne-safe sunscreenLa Roche-Posay Anthelios Clear Skin Dry Touch Sunscreen SPF 60

#4. Sunscreen For Combination Skin

Look for gentle and gel-like sunscreens that have vitamin E and aloe, good for both oily and dry skin.

Best Aloe Vera with Methi-based sunscreen for Combination skin – COSRX Aloe Soothing Sun Cream SPF50 PA+++

How Long Can You Safely Stay Without Sun Protection

You can stay in the sun safely for approximately 10-15 minutes without sunscreen. However, it depends more on your skin color and the strength of the UV Index (UVI) on that day. 

  • For people with darker skin, this time can be extended up to 30 minutes. 
  • For lighter-skinned individuals, the time can be shortened to 10 minutes or less.

UV Index (UVI)

The UV Index is a measure of how intense the sun’s UV radiation is. The higher the UVI, the greater the potential for damage to the skin and eye. On days when the UV Index is high, it’s important to wear sunscreen.

According to the World Health Organization, the UV index ranges from 0 to 11+, with 0 representing “Low” and 11+ indicating “Extreme High.” 

UV index includes –

UV index

When the UV Index reaches 11 or more, it is important to take precautions to protect your skin from the harmful effects of UV radiation. For those with lighter skin, a maximum exposure time of 4 to 6 minutes should be allowed. For people with darker skin, 20 to 30 minutes should be allowed.

Tips To Protect Your Skin From The Sun Without Sunscreen

#1. Wear Sun-Protective Clothing 

To protect yourself from the sun, wear a long-sleeved shirt, and pants that cover your entire body. You can also wear a wide-brimmed hat for your eyes, ears, face, and neck, and sunglasses with UVA and UVB protection that reduce eye damage from sun exposure. 

#2. Limiting Direct Sun Exposure

Avoid direct exposure to the sun between 10 a.m. and 4 p.m., when UV levels are strongest. Try to limit your direct exposure to the sun by seeking out shade whenever possible.

#3. Carry An Umbrella 

When you go out in the sun, it’s important to carry an umbrella for better protection from the sun’s UV rays. 


You should apply sunscreen 30 minutes before going outside for maximum protection. Reapply sunscreen every 2 hours during peak sun exposure or sooner if swimming or sweating. It’s the best way to protect yourself from the sun’s harmful ultraviolet (UV) rays. Let me know your thoughts in the comments.

About Sarah Smith

Sarah Smith is the founder of the NourishWithStyle. She is a self-professed skin care junkie and has an experience of more than 8 years of in the skincare domain. She loves to do experimenting with the latest beauty products and trends to share with the readers.

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