The Complete Guide to SPF 50+ Sunscreen

Chapter 2

How Sunscreen Works: UVA vs UVB and Broad Spectrum

UVB burns the surface of your skin while UVA penetrates deeper and drives premature ageing, and a broad spectrum sunscreen SPF 50 is the only kind that defends against both. SPF on its own describes only the UVB side of that equation, which is the single most important thing to understand about reading a label.

• UVB: shorter wavelength, surface-level, the main cause of sunburn and the radiation that SPF actually measures.
• UVA: longer wavelength, penetrates deeper into the skin, drives wrinkling and long-term ageing, and is present year-round.
• Broad spectrum: a tested claim that the product protects against both UVA and UVB, not just the burning rays.

Because SPF says nothing about UVA, a high SPF number is no guarantee of UVA cover. You need the words "broad spectrum" on the pack as well. The US Food and Drug Administration explains the distinction and the rules behind the broad-spectrum claim in its over-the-counter sunscreen questions and answers.

Modern formulas reach broad spectrum in two ways. Mineral filters such as zinc oxide and titanium dioxide sit on the skin and scatter or absorb radiation across a wide range, while organic filters absorb specific wavelengths and convert the energy to a small amount of heat. Many sunscreens, including a good sun cream SPF 50, blend the two so the finished product covers the full UVA and UVB span without feeling heavy.

The practical takeaway is simple. When you compare two bottles, confirm both are broad spectrum first, then look at SPF, then look at water resistance. Skipping the broad-spectrum check is how people end up protected from sunburn but not from the ageing and deeper damage UVA causes.

Chapter 3

SPF 30 vs 50 vs 50+: The Real Percentages

SPF 30 filters about 96.7 percent of UVB and SPF 50 about 98 percent, a gap that looks tiny but is more meaningful than it first appears. The Cancer Council lays out these figures in its sunscreen basics, and they are the numbers worth memorising before you compare products.

Read the other way around, the difference is clearer. SPF 30 lets roughly 3.3 percent of UVB through, while SPF 50 lets about 2 percent through. The unblocked fraction is what reaches your skin, and moving from SPF 30 to SPF 50 roughly halves it. That is a genuine improvement, but it is not the same as "blocks twice as much" - both numbers block the large majority of UVB, and the headline percentages stay close together.

Two facts anchor the whole comparison. First, no sunscreen blocks 100 percent of UV, so even the best sunscreen SPF 50 leaves a small fraction getting through. Second, because of that, the word "sunblock" overstates what any product can do; the FDA no longer allows "sunblock" claims for exactly this reason, which is why you will see "sunscreen" on compliant labels even when people still say sunblock SPF 50 in conversation.

The honest conclusion is that the SPF number is a floor, not a finish line. The 96.7 versus 98 percent gap only holds if the product is applied at the lab-tested thickness, which almost nobody does in real life. That is why the next two chapters - how much to apply, and how often to reapply - matter more for your actual protection than the choice between 30, 50, and 50+.

Chapter 4

How to Apply Enough (the Teaspoon Rule)

Under-application is the single biggest reason sunscreen fails to deliver its rated protection. The Cancer Council benchmark is about 7 teaspoons, or roughly 35 mL, for a full adult body, with about 1 teaspoon for the face and neck alone, applied 20 minutes before you go out, as set out in its sunscreen advice.

1. Apply 20 minutes before sun exposure so the sunscreen lotion SPF 50 has time to bind to your skin.
2. Use about 7 teaspoons (35 mL) for a full adult body - roughly 1 teaspoon for the face and neck, and 1 teaspoon for each arm, each leg, the front, and the back.
3. Spread it evenly rather than rubbing it in until it disappears; a visible film is closer to the tested amount.
4. Do not skip the easy-to-miss spots: ears, lips, the back of the neck, the tops of the feet, and any thinning hairline.
5. Let it dry before dressing or heading into water.

The reason the teaspoon rule matters so much is that SPF testing uses a thick, standardised layer. Apply half as much and you do not get half the protection - you get substantially less, often well below the number on the bottle. So the most reliable way to actually receive SPF 50 protection from a body sunscreen SPF 50 is to apply the full amount, every time.

A practical habit helps here. Decanting roughly the right amount into your palm first, rather than dabbing straight from the tube, makes it far easier to hit the benchmark, especially for kids who are keen to get into the water.

Chapter 5

Reapplication and Water Resistance

You should reapply sunscreen every two hours, and immediately after swimming, sweating, or towelling off, no matter how high the rating. The Cancer Council's sunscreen advice is consistent on this: water resistance buys time in the water, but it never replaces the two-hourly habit on dry land.

This is where two regulators tell the story differently, and it is worth understanding the gap. The US FDA caps water-resistance claims at either 40 or 80 minutes, and a product must be labelled with the tested figure, as explained in the same FDA sunscreen Q&A. Australia's TGA tests water resistance to as long as 4 hours under the AS/NZS 2604:2021 standard, so an Australian 4-hour claim reflects a longer testing protocol than the US 80-minute maximum.

It is important to read that "4 hours" as a label and testing-standard difference, not a clinical promise that you can swim for four hours unprotected. The 4-hour figure is the longest water-resistance period Australia's standard tests for; it is a stronger label claim than the US 80-minute standard allows, but real-world swimming, sweat, and towel-drying all strip product, which is why the every-two-hours-and-after-water rule still applies. We unpack how these regimes differ in our explainer on TGA vs FDA vs EU sunscreen regulations.

The simplest rule to carry in your head: treat any water-resistance figure as a maximum under ideal conditions, set a two-hour reminder, and reapply the moment you come out of the water and dry off. A clip-on format makes that reapplication realistic when you are away from your bag.

Chapter 6

Choosing the Right SPF 50+ for Your Day

The best SPF 50+ is the one you will actually reapply, so match the format to how you spend your day rather than chasing the highest number. Our SPF collection puts the lotions, zinc sticks, and lip balms in the SPF 50+ band, with Silk Mineral at SPF 50, so the real decision is about feel, portability, and the activity in front of you.

Before you buy, run any sun cream SPF 50 through a three-point checklist:

• Broad spectrum - confirmed on the label, so you are covered for UVA as well as UVB.
• Water resistant - with a tested duration that suits your activity.
• SPF 50 or 50+ - the top band, applied and reapplied properly.

Then match the format to the day. A clip-on body sunscreen SPF 50 lives on a bag or belt loop for sport, school, and the beach, so reapplication actually happens. A silk mineral SPF 50 suits sensitive skin and wear under makeup. An SPF 50+ lip balm covers the spot most people forget entirely. Picking the format you will keep within reach beats picking the one with the most impressive-sounding claim.

This is where our own story is relevant rather than a sales pitch. Standard Procedure's SPF 50+ sunscreen is broad spectrum and tested to Australia's AS/NZS 2604:2021 standard through the TGA with 4-hour water resistance - a longer testing standard than the US 80-minute maximum, presented as a label and testing-standard difference rather than a clinical guarantee. We are Australian-made on the Sunshine Coast and family-owned across three generations, and the Clip-On SPF 50+ starts at $14.99 precisely so the format that makes reapplication easy is also the one you can keep buying. You can read how we got here on our about page.