Sunscreen SPF: Is the Number Really Important?
SPF number is often treated as the most important factor in sunscreen – but is it?
Walk down any sunscreen aisle, and you’ll see numbers competing for attention: SPF 15, 30, 50, 70… and now even 100.
It’s easy to assume that the higher the number, the better the protection. But is that actually true?
Let’s break it down.
What Does SPF Actually Mean?
SPF stands for Sun Protection Factor. It measures how well a sunscreen protects your skin from UVB rays — the type of ultraviolet radiation mainly responsible for sunburn and a contributor to skin cancer.
Here’s what those SPF numbers really mean in simple terms:
• SPF 15 → blocks ~93% of UVB rays
• SPF 30 → blocks ~97%
• SPF 50 → blocks ~98%
• SPF 70–100 → blocks ~99%
So… Does SPF 70 or 100 Protect You Twice as Much as the rest?
Short answer: No.
This is one of the most common sunscreen misconceptions. SPF numbers don’t increase protection in a dramatic, linear way. While higher SPF does offer slightly more protection, the difference is modest, not mind-blowing.
In fact, the difference between SPF 30 and SPF 100 is only about 1–2%. Much smaller than most people expect — and definitely smaller than marketing often makes it seem.
Is Higher SPF Always Better?
Not necessarily.
No sunscreen blocks 100% of UV radiation, no matter how high the SPF. Very high SPF products can sometimes create a false sense of security, leading people to:
• Reapply less often
• Stay in the sun longer
• Assume they’re protected all day
But sunscreen doesn’t work that way.
Sweating, swimming, and just going about your day all break down protection. On top of that, most people apply less than half the recommended amount.
So even if you’re using SPF 100, in real life you may only be getting protection closer to SPF 30 or less.
Then, Why Does Higher SPF Exist?
Higher SPF does have a place. It can be helpful if you have:
• Very fair or sun-sensitive skin
• A history of skin cancer
• Prolonged outdoor exposure
• High-UV environments (beach, mountains, tropics)
It also provides a small margin of error, since under-application is so common. In everyday use, higher SPF often ends up performing closer to SPF 30 anyway.
The Bigger Issue: How You Use Sunscreen
Here’s the real takeaway:
How you apply sunscreen matters more than the SPF number.
For proper protection:
• About one ounce (a shot-glass amount) is required for the full body
• Use 2–3 full finger lengths for the face and neck
• Apply 15–20 minutes before sun exposure
• Reapply 3-4 hours once or every 2 hours, after swimming or sweating
A high SPF applied too thinly or only once a day protects far less than an SPF 30 used correctly.
The Real Game-Changer: Broad-Spectrum Protection
Instead of getting caught up in SPF numbers, it’s more important to choose a sunscreen that offers broad-spectrum protection.
Why? Because SPF only measures UVB protection. It tells us nothing about UVA rays, which penetrate deeper into the skin and play a major role in aging and skin cancer.
The UVA Problem
UVA rays don’t cause sunburn, but they’re no less harmful. They contribute to:
• Premature aging (wrinkles, sagging skin)
• Hyperpigmentation
• Skin cancer, including melanoma
That means a high-SPF sunscreen without good UVA coverage can still leave your skin vulnerable to long-term damage.
This is why “broad-spectrum” labelling is essential.
A broad-spectrum SPF 30 or higher is often more protective overall than an SPF 70 or 100 that lacks strong UVA protection.
So, What Should You Look for?
When choosing sunscreen, skip the SPF arms race and focus on:
• Broad-spectrum protection (UVA + UVB clearly stated)
• Ingredients with stable UVA coverage, such as zinc oxide
• Water resistance, especially for outdoor activities
• A formula you actually enjoy using — non-greasy, invisible, comfortable
The best sunscreen is the one you’ll:
• Apply generously
• Reapply regularly
• Use every day
A gentle reminder:
Sun protection isn’t about the highest SPF—it’s about smart habits. No single method of sun protection works perfectly on its own.
Sunscreen is just one key part of a smart sun-safety strategy, which also includes:
• Seeking shade
• Wearing protective clothing
• Using hats and sunglasses
SPF ratings are useful — but incomplete. They measure only UVB protection, not UVA, and they don’t reflect how real people actually use sunscreen. The better approach is a balanced, broad-spectrum sunscreen that fits your lifestyle and supports everyday use.
