SPF 50 can be a task master to rub in ‘eh. Sunscreen is the cheapest anti-ageing cream available, so making it easy to use every day is very important. Why buy an SPF 50 you’re going to find 102 excuses not to use, which brings us to the question: SPF 30 vs. 50 – is the 20 point jump up in SPF really worth it?
Will SPF 50 give you a whopping 40% more sun protection than SPF 30?
When comparing SPF 30 vs. 50 will the harder rub in be worth it?
How long does SPF 30 last? How long does SPF 50 last? Does SPF 50 last longer than SPF 30?
Here’s the thing my friend, the SPF scale is not like a ruler. Rulers are beautifully predictable, 1cm is 1cm and 10cm is 10 times bigger than 1cm. The same logic is not spreadable to SPF sun protection. Come see what I mean… and after, I promise you’ll know all the answers to any SPF 30 vs 50 question. Now that’s a party trick ‘eh.
Sunscreen SPF levels
SPF stands for sun protection factor and is the one sunscreen rating you’ll find pretty much the whole world over. It’s the IT rating of your sun cream party… making understanding what it means, especially important for choosing sun protection that A) works and that B) Is exactly what you’re looking for.
The SPF world is full of numbers, with sunscreen bottles sporting anything from SPF 2 (yes, really!) to SPF 110.
The higher the number, the better sun protection your skin receives… to a point, and it’s this point that I’ll explain very soon.
First, it’s important to know exactly what SPF sunscreens protect your skin against… because there’s 2 kinds of damaging UV light to be cautious about – UVA and UVB. Now, this isn’t a commonly known fact, but SPF sun protection only rates your skins protection against one of these 2 kinds of light. Which makes choosing sun protection based only on SPF levels, like going for dinner and only ordering dessert – It’s the best bit I know, but somehow having savoury before it, makes the desserty sweetness taste even better.
… but before chocolate fantasy’s devour us, let’s get back to sunscreen.
SPF my friend, only rates your skin’s protection against UVB light. UVB light is the kind that causes sunburn. UVA is the kind that causes premature ageing.
If you don’t have time to go into those in’s and out’s today I have some great sunscreen recommendations for you very soon – which you guessed it, protect your skin against both.
What is SPF 50?
To explain what SPF’s really mean, it’s easiest to use an example, so welcome to the floor… SPF 50. When a sunscreen has an SPF rating of 50, it’s telling us that only 1 in every 50 UVB rays will be allowed through to interact with your skin.
Which means… ready for a little quick math?
If 1 in every 50 UVB rays can interact with your skin, (1/50) x 100% = 2% of UVB rays are allowed to say hello.
Did you follow that?
So, we said 1 out of every 50 UVB rays, which in maths terms is 1 divided by SPF 50 and then to make this into a percentage, we multiply by 100, which leads us to find out that sunscreens with SPF 50 allow 2% of UVB light through.
…or in other words, an SPF of 50 provides 98% UVB protection. Pretty good ‘eh, but how does it compare to SPF 30? Here comes the interesting part.
SPF 30 vs 50
Sunscreens with SPF 30, tell you your skin is protected against 29 of every 30 UVB rays, or you guessed it… only 1 in every 30 UVB rays are allowed to say hello to your skin.
But what you’re really interested in is whether SPF 30 vs 50 gives you a 40% power-up in sun protection ‘eh. Because let’s level, many SPF 50 sunscreens take a wee while to rub in and like the savvy you are, you want to know whether that wee while is better spent being an awesome superwomen somewhere else.
Here’s the deal. And the math.
(1/30) x 100% = 3.33% which means 3.33% of UVB rays are allowed through a full (more about this soon) application of SPF 30 sunscreen.
Which also means SPF 30 gives your skin a protection percentage of 96.67, or rounded up 97%.
How Long Does SPF 30 Last?
Sunscreen which doesn’t contain physical filters like zinc oxide or titanium dioxide, gets used up. It’s used up because in order to stop UV light reaching your skin, it reacts with it and once all the sunscreen molecules have reacted, there’s no salt left in your salt shaker.
There’s a general saying that SPF 30 sunscreens will keep your skin protected for 30 times longer than it would normally take you to burn.
However. There’s more to consider;
- Sunlight is most intense around the hours of 10am-2pm
- Altitude increases the intensity of UVB light
- The angle of incidence increases UVB intensity e.g. if you’re in a country near the equator, receiving sunlight almost directly from the sun, your UVB intensity is high
- Glass blocks most UVB light i.e. if you’re indoors your UVB exposure is less (…but not your UVA exposure, making sun protection just as important)
- Sunscreen is easily rubbed off – the skin cancer foundation advise not to assume your sun protection is effective if its been longer than 2 hours since application aka reapply every 2 hours
Have you every burned so much more easily on holiday? Altitude and angle of UV incidence is why. Have you only burned in strips right next to the sides of your clothes? Sunscreen being easily rubbed off is why. Have you ever gotten a sunburn after only a quick walk outside at lunch? Sunlight being the most intense at midday is why.
— Cheryl Woodman (@HonestyForSkin) 31 July 2017
How Long Does Sunscreen Last After Applied?
Another very important SPF 30 vs 50 sunscreen consideration is the amount you apply. Because without applying the same amount scientists use to test for SPF in the lab, your skin is not going to be receiving the SPF stated on the bottle.
It’s like the difference between adding a smidgen or a great big dollop of milk to a cup of tea. It makes a great big difference ‘eh.
The magic sunscreen quantity is 2mg/cm2 which is about a quarter teaspoon for a full face application. This amount of sunscreen, gives you the stated SPF on your sunscreen bottle.
Now, here’s where it gets interesting.
Applying less sunscreen gives you less protection. However applying only the half the amount of SPF 50 gives you considerably more sun protection than applying half the amount of SPF 30.
Which means, if you know you’re not great at applying a full application of sunscreen (most people apply between 0.39 to 1.0 mg/cm2), SPF 50 may be your better bet.
This is another reason why it’s recommended to reapply your sunscreen every 2 hours.
SPF 30 vs 50 Sunscreens I Recommend
While knowing whether SPF 30 or SPF 50 is the best option for you, finding sunscreens worth their pennies in protection, is another question altogether. Sunscreen shelves can be even more confusing than skincare ones. Fear not dear friend, here are some great recommendations to get you started;
For an effective sunscreen with a high-street price tag;
- Soltan Sensitive Suncare Lotion SPF30 (£6.50/200ml)
- Soltan Baby Lotion SPF 50 (£6.50/200ml) – yes it says for baby but your skin deserves ultra-sensitive too
- A make-up bag sized go to for Face Soltan Sensitive Face Cream SPF50+ (£6/50ml)
For a sunscreen partnered with a super clean ingredients list;
- Green People’s Scent Free Sun Lotion SPF30 (£22/200ml)
- Odylique Natural Sun Screen for Sensitive Skin SPF30 (£25/100ml)
- SPF 50 protection for face BioSolis Extreme Fluid – SPF 50+ (£13.50/40ml)
Oh and if you don’t go for one of these beauties, be sure to download your free 1-page crib sheet to sun protection here, because while all of the above sunscreens protect your skin against both UVB and UVA light you’ll want to make sure any others you consider do too. That’s how you say goodbye to sun induced wrinkles.
So my friend, which is it for you? Do you now know the answer to your SPF 30 vs 50 dilemma? Still have questions? Ask them to me in the comments below…
Cheryl Woodman is a scientist & award winning skincare formulator who’s more friend next door than bow tie wearing professor. As creator of Honesty For Your Skin her aim is to help you care for your skin in the best ways possible. She’s founder of the natural & fragrance free skincare brand Honesty while also hosting 1 to 1 skincare coaching to help you get your best skin yet. Find out more here.