Category
Skin Health
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.
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.
What a Sunburn Really Is (and Why Prevention Beats Any Cure)
A sunburn isn't just pink skin — it's a visible sign of DNA damage and an inflammatory response that has to run its own course. Here's what's actually happening under the skin, why redness shows up late, why it can't be undone once it starts, and why the tools on this site exist to help you avoid one in the first place.
How Much Sunscreen Each Body Area Actually Needs
'A shot glass for the whole body' is the right rule, but it hides how unevenly that shot glass should be split. Here's the rule-of-nines math behind the Sunscreen Amount Calculator, worked out region by region — face and neck, arms, torso, and legs — in grams and teaspoons.
What the UV Index Actually Means, Hour by Hour
A single daily UV index number hides how dramatically the risk changes from 7 AM to 1 PM to 7 PM. Here's a worked example running one representative summer day's UV curve through the UV Index Safe-Exposure Calculator, hour by hour, for fair skin.
Vitamin D and Sun Exposure: What the Numbers Assume
The Vitamin D Sun-Exposure Estimator is not a dosing tool and isn't meant to be read as one. Here's what its numbers actually represent — how skin type and how much skin is bare change the estimate — and why a blood test and a doctor, not a calculator, are the only way to know where you stand.
Sun Protection for Babies and Kids: Clothing, Shade, and Sunscreen Basics
Children's smaller bodies and thinner skin change the sunscreen math and shorten the safe-exposure window — and shade and clothing, not sunscreen, are usually the first line of defense. Here's how the site's calculators apply to a child's body, and where this article stops and a pediatrician's advice starts.