SUNSTOKE
Smart in the sun — SPF know-how, safe tanning, and protecting your skin without hiding indoors.
From knowing when your sunscreen has worn off and how long your skin can safely stay out, to how much to actually apply, whether a tan session is sensible, and today’s real burn risk, SunStoke pairs free hands-on calculators with plain-spoken guides and an illustrated museum of the sun and skin. Enjoy the sun; protect your skin. This site is general information, not medical or dermatological advice.
Sun-Safety Tools & Calculators
Free tools for staying safe in the sun — SPF reapplication timer, UV-index safe-exposure calculator, sunscreen amount calculator, tan-session estimator, vitamin-D estimator, and a sunburn risk score.
SPF Reapplication Timer
Find out when your sunscreen has worn off. Enter when you applied and whether you've been swimming or sweating to get your next reapplication time — because protection fades with water, towels, and time, not the number on the bottle.
UV Index Safe-Exposure Calculator
Estimate how long unprotected skin can stay out before it burns, based on today's UV index and your skin type — then see how much longer a given SPF buys you.
Sunscreen Amount Calculator
Work out how much sunscreen you actually need using the dermatologist's 2 mg/cm² rule — grams, teaspoons, and 'shot glasses' for the body areas you're covering, per application and per day.
Tan Session Time Estimator
Find a sensible time limit for building colour gradually without burning, based on the UV index, your skin type, and any SPF — plus an honest note on which skin types shouldn't chase a tan at all.
Vitamin D Sun-Exposure Estimator
Estimate the short midday exposure that may support vitamin D synthesis, given the UV index, your skin type, and how much skin is uncovered — well short of a burn, and no substitute for a blood test.
Sunburn Risk Score
Score today's burn risk from the UV index, your skin type, time outside, SPF, altitude, and reflective surfaces like water, sand, and snow — a quick Low-to-Extreme read before you head out.
The Sun & Skin Museum
Wander an illustrated museum of the sun and the skin it shines on — the star at the centre of our sky, the biology of human skin, the long history of sunscreen and cosmetics, and the ultraviolet light that makes protection matter, each in its own gallery, so you can get to know the science behind every sunny day: what the sun actually does, how skin responds, and why the right habits keep you safe.
Tour the museum →From the Journal
Plain-language guides on how SPF works, chemical versus mineral sunscreen, how much to apply, reading the UV index, safe-tanning myths, protecting skin by type, and sunburn first aid — all general information, never a substitute for a professional.
How SPF Actually Works (and What the Number Really Means)
SPF isn't a timer and it isn't a percentage of 'strength' — it's a ratio measured in a lab. Here's what SPF 15, 30, and 50 really block, why 'broad spectrum' matters, where the minimal erythema dose comes from, and why the number on the bottle is only half the story.
Chemical vs Mineral Sunscreen: Which Should You Use?
Chemical and mineral sunscreens protect your skin in different ways — one absorbs UV, the other reflects and absorbs it. Here's how each works, their real pros and cons, how they hold up in makeup and water, and how to pick the one you'll actually wear and reapply.
How Much Sunscreen to Apply — The Amount Almost Everyone Gets Wrong
The single biggest reason sunscreen underperforms isn't the SPF you chose — it's using too little. Here's the 2 mg/cm² rule in plain teaspoons and shot glasses, how far a bottle should actually last, and how to cover the spots people always miss.
Understanding the UV Index: How to Read It and What to Do
The UV index is a free daily forecast of how fast the sun can damage your skin — yet most people scroll past it. Here's what the 0-to-11+ scale means, where the forecast comes from, what raises it, and the simple actions each band calls for.
Safe Tanning Myths, Debunked
A 'base tan,' the idea that tanning beds are safer, the belief that you can't burn on a cloudy day — the myths around tanning are stubborn and risky. Here's what the evidence actually says, and what a genuinely more cautious approach to time in the sun looks like.
Protecting Your Skin by Type: A Guide to the Fitzpatrick Scale
Not all skin responds to the sun the same way. The Fitzpatrick scale sorts skin into six types by how it burns and tans — here's what each type means for how you protect yourself, how to place yourself on it, and why no type is exempt from sun protection.
Keep Learning
Plain-language explainers on the sun and ultraviolet light, how the sun affects your skin, the ways to protect it, and the truth about tanning and vitamin D — everything you need to make sense of the science and stay safe.
Visit the Learn hub →