How much sunscreen to apply, how and when: the complete guide

Almost everyone applies less sunscreen than they should, and therefore gets far less protection than the label promises. The reference dose is two milligrams per square centimetre of skin. In practice: two finger-lengths for the face and neck, and about a teaspoon for each area of the body — each arm, each leg, front of torso, back of torso. Reapply every two hours in direct exposure. Applying half the dose does not give half the protection: it gives far less.

How much sunscreen should I apply to my face?

Two finger-lengths — the two-finger rule. Squeeze product along the index and middle fingers, from the base of the nail to the base of the finger. That amount covers face and neck.

By volume, it corresponds to roughly a third to half a teaspoon for the face alone.

It is considerably more than most people use. If a bottle lasts you months, you are applying too little.

One detail changes everything: protection is not proportional to quantity. Applying half the dose of an SPF 50 does not give SPF 25 — it gives something closer to SPF 7. This is why quantity matters more than the number on the bottle.

How do I apply sunscreen to my face?

Apply to clean, dry skin, before makeup.

Distribute in small dots across the face and spread. Do not rub hard — friction reduces the evenness of the layer.

The most forgotten areas, in order: ears, neck, nape, around the eyes, lips and scalp along the parting or in thinning areas. For lips, use a stick with SPF.

Wait two to three minutes before applying anything on top.

When should I use sunscreen?

Every day, all year round, including cloudy days and days spent indoors.

UVA radiation passes through cloud and glass. It is the main driver of photoageing and contributes to skin cancer. Sitting by a window is exposure.

Apply in the morning, as the last step of your skincare and before makeup. If you go out, reapply every two hours in direct exposure, and always after swimming, sweating or towelling dry.

On an indoor working day with little window exposure, a single morning application is usually enough.

Which sunscreen should I use?

The criteria to look for, whatever the brand:

• SPF 30 minimum, and 50+ for fair skin types, melasma, rosacea or a history of skin cancer

• UVA protection — the UVA symbol in a circle, mandatory in the European Union

• A texture you like, because the best sunscreen is the one you actually use every day

• Non-comedogenic, if you are prone to acne

For the face, a dedicated facial product tends to have a better texture and is less likely to block pores than a body formula.

Oily or acne-prone skin: gel, fluid or serum textures, marked non-comedogenic, with a matte finish.

Sensitive skin or rosacea: mineral filters with zinc oxide or titanium dioxide, fragrance-free.

Melasma or pigmentation: a tinted filter, because the pigment — usually iron oxide — also blocks visible light, which transparent filters do not stop and which drives pigmentation.

Children: mineral filters from six months of age. Below that, the recommendation is to avoid direct exposure and use clothing and shade rather than product.

Does SPF 100 exist? Is it worth it?

It exists in some markets, but the gain is marginal and the number misleads.

SPF 30 blocks around 97% of UVB radiation. SPF 50 blocks around 98%. SPF 100 blocks around 99%. The difference between 50 and 100 is one percentage point.

In the European Union, labelling does not permit values above 50+, precisely because they would mislead.

The risk is behavioural: people using a very high number tend to feel protected and stay in the sun longer without reapplying. A well-applied and reapplied SPF 50 protects more than an SPF 100 applied once in the morning.

Mineral or chemical sunscreen? And the “natural” ones?

Mineral filters (zinc oxide, titanium dioxide) work mainly by reflecting and scattering radiation. They are well tolerated on sensitive skin and work immediately on application, but can leave a whitish cast, particularly on deeper skin tones.

Organic filters, often called chemical, absorb radiation. They have a lighter texture and leave no white residue. They are equally safe and effective.

The term “natural” has no regulatory definition in cosmetics. A mineral filter may be described as natural, but the zinc oxide used in cosmetics is industrially produced.

What does not exist is effective sun protection from vegetable oils. Coconut, raspberry seed or carrot oil have no meaningful SPF, and they circulate on social media as alternatives. They are not.

What does sunscreen actually do?

Three things, in order of clinical importance.

Prevents skin cancer. Regular use reduces the incidence of squamous cell carcinoma and melanoma. It is the main reason, though rarely the one that makes someone buy it.

Prevents photoageing. Ultraviolet radiation causes most of the wrinkling, laxity and pigmentation attributed to age. Comparing the skin of the face with the inner arm, in the same person, demonstrates this better than any explanation.

Prevents and controls pigmentation. In melasma and post-inflammatory hyperpigmentation, sun protection is not an accessory: without it, no lightening treatment works.

The most frequent mistakes

• Applying too little — the most common of all

• Not reapplying during the day

• Using it only on sunny days or at the beach

• Forgetting ears, neck, hands and lips

• Relying on the SPF in foundation, which is rarely applied in sufficient quantity

• Applying it after already being in the sun

• Using last year's product past its date or poorly stored in heat

When to speak to a dermatologist?

• When you have pigmentation, melasma or rosacea and need a filter suited to your case

• When sunscreens give you spots or irritation

• When you have skin type I or II, many moles or a family history of melanoma

• When you have had blistering sunburn, particularly in childhood

• When a mole has changed in size, colour or shape

Dr Ellene Papazis is a dermatologist accredited in Portugal and Brazil, with training in cutaneous oncology, and performs mole mapping in Porto, Portugal.

Sources

• American Academy of Dermatology — sun protection recommendations

• Regulation (EC) No 1223/2009 on cosmetic products — EU sun protection labelling

• European Academy of Dermatology and Venereology

• Portuguese Society of Dermatology and Venereology (SPDV)

Written and reviewed by Dr Ellene Papazis, dermatologist accredited in Portugal and Brazil. Consultations in Porto, Portugal.

Updated 25 July 2026.