Guide

How often should you reapply sunscreen?

Reapply sunscreen at least every two hours when you are outdoors, and straight away after swimming, sweating heavily or towel drying. That rule comes from the FDA and the American Academy of Dermatology, and it applies whatever the SPF number. Here is how it works on beach days, office days and makeup days.

Every 2 hours outdoors Right after swimming or sweating Higher SPF does not last longer

OutdoorsAt least every 2 hours

Water or sweatReapply right after

Water resistant40 or 80 minutes, then reapply

Mostly indoorsMorning layer, reapply before going out

The short answer

How often should you reapply sunscreen? At least every two hours while you are outside, and immediately after swimming, heavy sweating or towel drying, according to the FDA and the American Academy of Dermatology. Water-resistant sunscreens are only tested to hold up for 40 or 80 minutes in water, and a higher SPF does not last longer, so neither changes the rule. If you spend the day indoors away from windows, one generous morning application is usually enough; reapply before you head outside.

Key takeaways

Reapply at least every two hours outdoors, and right after swimming, sweating or toweling off, even with water-resistant sunscreen.
SPF 50 does not last longer than SPF 30; it blocks slightly more UVB but wears off on the same schedule.
Reapplying only works if you use enough each time: about a shot glass for the body and at least a teaspoon for the face.

The rule

How often to reapply sunscreen: the 2-hour rule

The FDA advises reapplying sunscreen at least every two hours, and more often if you are swimming or sweating. The AAD gives the same advice and adds that you should reapply immediately after getting out of the water or sweating, even if your sunscreen is water resistant. Most US sunscreen labels repeat it in their Drug Facts directions; a typical label reads “reapply at least every 2 hours,” as on the US Round Lab sunscreen we cover in Beauty of Joseon vs Round Lab sunscreen.

Two other timing rules sit alongside it:

Apply first, then go out. Both the FDA and the AAD suggest applying about 15 minutes before sun exposure.
Water resistance has a time limit. FDA rules require “water resistant” labels to say whether protection lasts 40 or 80 minutes while swimming or sweating. No sunscreen is waterproof or sweatproof.

Situation	When to reapply	Why
Outdoors, dry	At least every 2 hours	FDA and AAD guidance; sunscreen rubs, sweats and wears off.
Swimming	As soon as you get out, and at least by the 40- or 80-minute mark on the label	Water resistance is time-limited.
Heavy sweating or sport	Right after, or every 40 to 80 minutes with a water-resistant product	Sweat and wiping remove sunscreen.
After towel drying	Immediately	Towels physically wipe sunscreen off.
Indoors, away from windows	Before you go outside	Little UV exposure indoors.
Indoors, by a sunny window or driving	Consider every 2 hours on long exposures	The AAD notes UVA passes through window glass.

Why it wears off

Why do you need to reapply sunscreen?

Sunscreen does not stop working on a timer, but the layer on your skin gets thinner through the day. Sweat, water, rubbing, touching your face and towel drying all remove it. Because protection depends on how much is left on your skin, an under-applied or worn-down layer gives far less than the SPF on the bottle.

Does SPF 50 last longer than SPF 30? No. The AAD explains that SPF 30 blocks about 97% of UVB rays, and higher numbers block slightly more, but higher SPFs do not last longer. The FDA also cautions that SPF does not mean you can stay in the sun proportionally longer. See SPF 30 vs SPF 50 for when the higher number is worth it.

Amount matters as much as timing. The AAD suggests about one ounce, roughly a shot glass, to cover exposed skin for most adults, and at least a teaspoon for the face. Our guide to how much sunscreen to use breaks this down by body area.

Real-life days

How often to reapply sunscreen at the beach, at work and in winter

Beach or pool

Every swim, every 2 hours

Use a water-resistant, broad-spectrum SPF 30+. Reapply after every swim and towel dry, and by the 40- or 80-minute mark on the label. Add shade, a hat and a rash guard. If you do burn, see sunburn for care.

Office or home day

One good morning layer

If you stay indoors away from windows, a generous morning application is usually enough. Reapply before lunch outdoors, your commute, or long periods next to a sunny window.

Sport and workouts

Water resistant, reapply often

Sweat removes sunscreen. Choose a water-resistant formula and reapply right after heavy sweating. A stick or spray can make it easier on the go; see spray vs lotion sunscreen.

Cloudy days and winter

Same rule outdoors

The AAD notes UV rays reach your skin on cloudy and cold days too, so the 2-hour rule applies whenever you are outside for long.

Melasma or dark spots? If you are treating pigmentation, stricter sun habits matter more. Our melasma guide explains why visible light and window exposure can matter, and our tinted vs untinted sunscreen comparison covers tinted options.

Step by step

How to reapply sunscreen (including over makeup)

Blot first
Gently blot sweat and oil with a tissue so the new layer spreads evenly.
Use the same amount again
Reapplying a thin film does little. For the face, aim for about a teaspoon again.
Do not forget the easy-to-miss spots
Ears, back of the neck, hairline, tops of feet, hands and lips (use an SPF 30+ lip balm, as the AAD suggests).
Over makeup: choose a format you will actually use
Pat on a sunscreen lotion with a damp sponge, mist a face sunscreen spray (not directly into your face; spray into your hands first), or use a sunscreen stick. SPF powders and makeup alone are usually too thin to count; see is SPF in makeup enough?
Sprays: apply until skin glistens, then rub in
The AAD advises spraying until skin glistens, rubbing it in, and avoiding spraying into wind or near heat or flame.
Set reminders
On long outdoor days, a phone alarm every two hours is the simplest way to stay on schedule.

If your morning sunscreen pills or feels heavy under makeup, our sunscreen under makeup guide has layering tips.

Common mistakes

Sunscreen reapplication mistakes to avoid

Do

Reapply at least every 2 hours outdoors and after every swim.
Use broad-spectrum SPF 30 or higher.
Keep a travel-size sunscreen in your bag.
Check the expiry date; see does sunscreen expire?
Combine sunscreen with shade and clothing, especially between 10 a.m. and 2 p.m., as the FDA advises.

Avoid

Assuming high SPF means you can skip reapplying.
Trusting “all-day” or “sweatproof” wording; no sunscreen is sweatproof.
Using a much thinner layer when you reapply.
Leaving sunscreen in a hot car, which the AAD says speeds breakdown.
Relying on SPF makeup or moisturizer for long outdoor days.

Safety and professional-help boundaries

When sun protection is a medical question.

Do not use sunscreen on babies under 6 months without asking a doctor; the FDA advises shade, clothing and avoiding peak sun instead.
Blistering sunburn, fever, chills or feeling unwell after sun exposure need medical attention.
If you take medicines that make skin sun-sensitive, or have a photosensitivity condition or history of skin cancer, ask your doctor about extra protection.
A new, changing, itchy or bleeding spot should be checked by a dermatologist.
In pregnancy, our pregnancy skincare guide favors mineral sunscreen (zinc oxide or titanium dioxide); the reapplication rules are the same.