A sunscreen label gives you two ratings and a lot of marketing. Only the ratings are measured to a set method, so they are the place to start. The catch is that each one answers a narrow question, and people often expect more from them than they can deliver.
If you want the full buying picture, including textures and filters, see our guide to choosing a sunscreen in India. This article sticks to the numbers.
What SPF is measuring
SPF stands for sun protection factor. In a lab, researchers compare how much UV it takes to redden skin with and without a sunscreen layer of 2 mg per square centimetre. The ratio between the two is the SPF.
The scale doesn’t climb in a straight line. Doubling the number does not double the protection:
| SPF | Approx. UVB blocked (lab conditions) | Approx. UVB getting through |
|---|---|---|
| 15 | ~93% | ~7% |
| 30 | ~97% | ~3% |
| 50 | ~98% | ~2% |
Look at the last column rather than the middle one. Moving from SPF 30 to SPF 50 cuts the UVB reaching your skin by around a third or more in lab conditions. That is real, but small next to the loss from applying a thin layer, which most people do. A well-applied SPF 30 can easily outperform a skimpy SPF 50.
The “minutes in the sun” myth
You may have heard that SPF 30 lets you stay out 30 times longer than bare skin. Please don’t use the number as a timer. It ignores sweat, rubbing, uneven application and the strength of the sun on a given day. A May afternoon in Nagpur and a December morning in Shimla are very different exposures, and the bottle doesn’t know which one you’re in.
What PA is measuring
PA stands for protection grade of UVA. It comes from a test called persistent pigment darkening (PPD), which measures how much UVA it takes to cause lasting skin darkening with and without sunscreen.
| PA rating | Commonly used PPD range | Level of UVA protection |
|---|---|---|
| PA+ | 2 to 4 | Some |
| PA++ | 4 to 8 | Moderate |
| PA+++ | 8 to 16 | High |
| PA++++ | 16 or more | Very high |
PA matters a great deal for Indian skin. Melanin-rich skin tends to respond to sun by producing more pigment, so UVA is closely linked to tanning, melasma and the dark marks acne leaves behind. UVA is also present through much of the day, in most seasons, and passes through ordinary window glass. Our article on sunscreen indoors and in the monsoon looks at that in more detail.
Other words you may see instead of PA
Not every sunscreen sold in India uses the PA system, especially imported ones. These labels point to the same kind of protection:
- Broad spectrum: the sunscreen has passed a test showing UVA as well as UVB coverage. The standard differs by country.
- UVA in a circle: a European mark, meaning the UVA protection is at least a third of the labelled SPF.
- PPD number: some labels print the figure itself. Compare it with the table above.
A vague phrase such as “UV shield” or “sun defence” tells you nothing. Treat it as decoration unless a rating sits beside it.
What neither rating covers
Three common assumptions go beyond what the numbers can tell you:
- Visible light. SPF and PA say nothing about it, yet visible light can worsen pigmentation in darker skin tones. Tinted sunscreens with iron oxides offer some help here.
- Staying power. A rating describes a fresh, thick layer, not how the sunscreen holds up after an hour on a scooter in the humidity. “Water resistant (40 or 80 minutes)” is the only label wording that speaks to this, and it covers water and sweat rather than a full day.
- Your application. Lab results use a generous, even layer. Our guide to how much sunscreen to apply shows what that amount looks like on your fingers.
Matching the numbers to your day
These are starting points, not strict rules:
| Your day | Reasonable rating |
|---|---|
| Mostly indoors, away from windows, short trips outside | SPF 30, PA+++ |
| Desk beside a window, daily commute | SPF 30–50, PA+++ or PA++++ |
| Long hours outdoors, field work, beach or hill trips | SPF 50, PA++++, water resistant if you sweat a lot |
| Melasma, acne marks or pigmentation that darkens easily | SPF 50, PA++++, ideally tinted with iron oxides |
If two sunscreens have similar ratings, choose the one you like wearing. A rating helps only when the product actually reaches your skin in a thick enough layer, and many people cut back on a texture they dislike, especially in sticky weather.
Numbers that should make you pause
- SPF 100 or higher. The extra UVB protection over SPF 50 is slight, and the number can encourage people to apply less or stay out longer.
- SPF inside a moisturiser or foundation. The rating is genuine, but few people apply these thickly enough to reach it.
- A high SPF with no UVA claim. This leaves out the protection most tied to pigmentation.
Sunscreen is one layer of protection
No rating means total protection. During the harshest hours, usually from about 10 am to 4 pm, shade, a wide-brimmed hat or umbrella, sunglasses and loose full-sleeved clothing all reduce what sunscreen has to do. They also help where sunscreen tends to get missed or sweated off.
See a dermatologist if pigmentation keeps spreading or won’t fade, if a mole or spot changes in size, shape or colour, or if your skin reacts to sun or sunscreen with a rash or swelling. This article is general information and not medical advice.
Bottom line
SPF is your UVB number and PA is your UVA number, and Indian skin needs both. SPF 30–50 with PA+++ or higher covers most people. Beyond that, the amount you apply and how often you reapply will affect your protection more than a higher figure on the tube.
Frequently asked questions
Does SPF 50 last longer on skin than SPF 30?
No. SPF describes how much UVB gets through a properly applied layer, not how long that layer stays in place. Sweat, oil, rubbing and time wear down any sunscreen, so the usual advice of reapplying about every two hours outdoors applies to both.
Do I really need PA++++, or is PA+++ enough?
PA+++ is a sensible minimum for most Indian skin. PA++++ is worth choosing if you tan or pigment easily, have melasma or acne marks, or spend long periods outdoors, as long as you like the texture enough to wear it generously.
What if my sunscreen has an SPF number but no PA rating?
Look for the words "broad spectrum" or a UVA symbol in a circle, which also indicate UVA protection. If the label shows none of these, you can't tell how well it protects against UVA, so it is better to pick another one.
Will a high SPF and PA rating stop me tanning completely?
No. No sunscreen blocks everything, and real-life application is usually thinner than the lab layer. Shade, a hat, sunglasses and covering up all add protection that sunscreen alone cannot give.
