SunDose
Product
Introducing SunDose: Glow Smarter, Tan Safer
Tanning is one of the last things we still do completely by feel. No timer, no real sense of how strong the sun is, and nothing that remembers what we did yesterday. SunDose is our answer to that — a calm, UV-aware companion for iPhone that helps you tan more safely and actually enjoy your time in the sun. Here’s what it does and why we built it.
Key takeaways
- SunDose turns time in the sun into a guided session built around the real-time UV index and your skin type.
- The WHO recommends sun-protection measures once the UV Index reaches 3 or higher (WHO) — SunDose surfaces that number before you head out.
- It’s free, iPhone-only, privacy-first, and available now on the App Store.
Why we built SunDose
We kept running into the same problem: you can check the weather for rain in seconds, but “how strong is the sun right now, and how long should I actually stay out?” has no easy answer. So most of us guess. We stay out a little too long, forget to reapply, or skip the sun entirely on a perfect day.
The app started as the one we wanted for ourselves. The goal was never to keep anyone indoors. It’s to add just enough awareness that a day in the sun feels intentional instead of accidental — and a lot less likely to end in regret.
What is SunDose?
SunDose is a free iPhone app that turns sun time into a guided session. It works in three simple parts: it reads the conditions around you, runs a timer built for your skin, and helps you keep the habit going with routines, reminders and a visual record of your progress. You can see the full feature tour on our home page.
Think of it as the difference between sunbathing blind and sunbathing with a dashboard. You still decide when to go out. The app just makes sure you know what you’re walking into.
How does SunDose read the UV around you?
SunDose shows the real-time UV index for your exact location, hour by hour, so you can see when the sun peaks and when the safer windows are. That matters, because the UV Index is the standard global measure of sunburn-causing radiation — and the World Health Organization recommends taking sun-protection measures once it hits 3 or higher (WHO, “Radiation: The ultraviolet (UV) index”).
Here’s the scale SunDose surfaces at a glance, based on the US EPA UV Index:
No more guessing whether it’s a three or a nine out there. You open the app, you see the number, and you make a better call about when to head out and when to wait.
A session timer tuned to your skin
The part we’re most proud of is the session timer. You tell SunDose your skin type and whether you’ve applied SPF, and it builds a session around the current UV. You start the timer, relax, and let the app keep time for you — including a Live Activity on your Lock Screen so you can glance at progress without opening anything.
Everyone’s skin responds to the sun differently, so the guidance adapts rather than handing everyone the same one-size advice. A fair-skinned afternoon at UV 8 is a very different session from an olive-skinned hour at UV 3, and the timer reflects that. The result is a tanning habit that respects how your skin actually behaves, not a stopwatch you have to babysit.
A routine that keeps your glow on track
Beyond the timer, SunDose helps you stay consistent. You get a personalized routine you can log, hydration tracking with gentle nudges on hot days, and skin-sensitivity flags for things like retinol, vitamin C or certain medications that can make skin more reactive to sun. None of it is preachy — it’s just there when you need it, and easy to ignore when you don’t.
Over time, it adds up. Streaks, a visual tan journey, and simple weekly insights show your exposure, your average UV, and the days worth being a little more careful on. Home Screen widgets put today’s UV, your streak and a one-tap start right where you’ll see them, so the habit sticks without any extra effort.
Built privacy-first, designed for iPhone
Your skin profile and sessions stay on your device. There’s no tracking and no profiles sold — you can read exactly how we handle data in our privacy policy. SunDose is built to be genuinely useful without nagging paywalls or data harvesting, and as a native iOS app, the Live Activities, widgets and interface all feel at home on iPhone.
And it’s free. We’d rather you actually use it every sunny day than bounce off a paywall the first time you open it.
Glow smarter, tan safer
We didn’t build SunDose to keep people out of the sun. We built it to help us enjoy the sun a little more aware, and a lot less likely to overdo it. If that sounds like something you’d use, download it on the App Store — and follow along on our social channels for more smart-tanning tips.
Sources
- World Health Organization, “Radiation: The ultraviolet (UV) index” — retrieved 2026-06-25, https://www.who.int/news-room/questions-and-answers/item/radiation-the-ultraviolet-(uv)-index
- US Environmental Protection Agency, “UV Index Scale” — retrieved 2026-06-25, https://www.epa.gov/sunsafety/uv-index-scale-0
Frequently asked questions
- Is SunDose free?
- Yes. SunDose is free to download on the App Store, with no subscription pressure or paywall gating the core experience. It's made for iPhone by Fios Apps.
- Does SunDose work anywhere?
- SunDose shows the real-time UV index for your current location, hour by hour. Because UV changes with time of day and place, the forecast updates so you can spot peak hours and safer windows before you head out.
- When is the sun strongest?
- UV is most intense around midday. A simple EPA check: if your shadow is shorter than you are, UV levels are higher and sun protection is wise. SunDose's hourly forecast makes those peak hours easy to see.
- Which iPhones does SunDose support?
- SunDose is an iPhone app with Live Activities and Home Screen widgets. Download it from the App Store to see compatibility for your specific device.