The Sun Doesn't Care
About Your Vacation.
At high UV, skin can burn in under 15 minutes, and you won't even notice. Suntan Workout tracks the UV index at your beach in real time, works out your safe time in the sun, and tells you out loud when it's time to turn over.
Front Side
Back Side
Left Side
Right Side
Shade RecoveryFront SideEngineered for the Beach.
High Contrast. Sandy Hands Approved.
Designed from day one to be legible under blinding midday beach sun, with oversized numerals, dark contrast modes, and voice coaching.
Adapts session minutes to real-time solar intensity
- Live UV Dose: Adapts session minutes to real-time solar intensity
- Circular Timer: Visual position arc with voice flip alerts
- 12-Session Ladder: Calibrated steps from 0.20 to 1.00 MED
- Custom Session: Set custom minutes for each of the 5 positions
- Beach Contrast Mode: Sharp black-and-gold visibility under glaring sun
How Long Can You Tan Today?
Your Burn Time at Today's UV.
Fixed timers lie. The sun delivers energy in Joules per square meter. At UV 8, an unadapted Type I burns in just 16 minutes. See your real numbers:
Past this point skin starts to burn. The app keeps every session well below it.
Eyes Closed. Phone In Bag.
Your Coach Tells You When to Flip.
Never get one-sided lobster burns or uneven zebra stripes again. Suntan Workout guides you through 5 balanced positions with loud audio chimes and Apple Watch haptic taps.
Apple Watch Wrist Taps
Keep your iPhone safe in your beach bag. The standalone Apple Watch app taps your wrist when it's time to rotate, displaying remaining seconds at a glance.
Live Activity & Lock Screen
No need to unlock your phone with sandy hands. The dynamic Island and Lock Screen timer count down in real-time, showing the current side icon.
The Magic of Shade Rest
Melanin synthesis does not require constant blistering heat. A 10-minute shade break halts UV radiation stress while cellular pigment develops safely.
Build Your Own Custom Session
Want 10 minutes on your back and 5 on your side? Custom session lets you set exact minutes per position whenever you want manual control.
A Workout For Your Melanin.
Step by Step. No Blisters.
Nobody runs a marathon on day one. Suntan Workout delivers ultraviolet dosage in a calibrated 12-rung training ladder. The first 4 sessions are 100% free.
Session 1 • 0.20 MED
0.20 MED — 80% below the burn threshold. Perfect for pale or post-winter skin.
4 Lethal Sun Myths
That Ruin Vacations Every Year.
Click any card to reveal why your instincts are burning your skin — and how the physics actually works.
"I got a base tan first, so I can safely lay in the sun for hours."
A deep base tan provides a natural sun protection factor equivalent to only SPF 2 to 3. That gives you less than 5 extra minutes of protection in high UV. You will still burn severely.
"It’s cloudy and overcast today, so there’s no way I will get sunburned."
Up to 80% of UV rays penetrate cloud cover. Worse, the 'cloud edge effect' acts like a lens, focusing scattered rays and increasing peak UV intensity by up to +25% over clear sky!
"Staying out twice as long will get me twice as dark."
Your skin's melanocytes have a daily biological production ceiling. Once saturated, additional radiation does zero extra tanning — it only causes cellular DNA mutation and skin peeling.
"I feel cool and the ocean breeze is fresh, so the sun isn’t intense."
Infrared radiation produces heat; ultraviolet radiation produces erythema and burns, but produces zero sensation of heat. You burn just as fast in 18°C as in 38°C under the same UV index.
No Pseudo-Science.
Pure Photobiological Physics.
We don't sell crystals or magic oils. Suntan Workout is built on the standardized CIE erythemal action spectrum and clinical Minimal Erythema Dose data.
How Your Seconds Are Calculated
// 1. Erythemally weighted solar irradiance (W/m²)
irradiance = UV_Index × 0.025
// 2. Exact session seconds for target MED fraction
seconds = (doseFraction × Skin_MED) / irradianceWhy Generic Timers Burn You
Start 100% Free.
Upgrade Only When You Love It.
No trial traps. No forced credit cards. Test the real physics engine for your first four sessions, completely free.
Free Foundation
Everything you need to test the science and build your baseline without burning.
- Sessions 1 to 4 (up to 0.33 MED)
- Live UV Satellite Adaptation (scaled automatically)
- 5-Position Rotation Coach with audio gongs
- Apple Watch App with wrist haptics
- 100% Guest Mode (no email or account required)
Suntan Workout Pro
For sun lovers who want complete 12-session conditioning and full control.
- Everything in Free, plus:
- Full 12-Session Ladder (reach peak 1.00 MED)
- Custom Session Builder (set minutes per position)
- Manual Location Picker (plan vacation spots)
- Cross-Device Cloud Sync (iPhone, iPad, Watch)
- Session History & Streak Tracking
Radical Privacy: Zero Ad Trackers, Zero Data Brokering
We deliberately removed Facebook SDK, TikTok SDK, and Firebase Analytics. We don’t ask for IDFA / ATT tracking permissions. Your skin reactions and health history are never sold to advertisers.
Everything You Need to Know
About Safe Sun Exposure.
Have questions about the algorithm, weather sources, or Apple Watch integration? We've got answers.
It depends on your skin type. Unadapted skin starts to burn after: at UV 5 — about 27 min (type I), 32 min (type II), 44 min (type III) and 57 min (type IV); at UV 8 — 17, 20, 28 and 36 minutes; at UV 10 — 13, 16, 22 and 29 minutes. A safe first session is only a fifth of that: about 4 minutes in total for type II skin at UV 8. Suntan Workout does this maths for your live UV and splits the time across positions.
Start well below your burn dose and build up gradually: Suntan Workout begins at 20% of it and adds a little each session. Turn over on schedule so no side gets the full dose, rest 10 minutes in the shade, keep sunscreen on your face, lips and tattoos, and don't move up a step if your skin turned pink the evening before.
You tan at any UV index from about 3 upwards. A higher index doesn't give a better tan — it only shortens the safe time. UV 3–5 is easiest for beginners: sessions are longer and easier to time. At UV 8 and above even fair skin burns in under 20 minutes, so keep sessions very short or tan in the morning and late afternoon.
The app fetches live hourly irradiance and UV index data from Open-Meteo based on your GPS coordinates or chosen city. It applies real-time solar zenith math and clear-sky cloud scaling to deliver exact erythemal flux calculations.
Wind does not reduce UV radiation — it only cools your skin, masking burning sensations. For clouds, up to 80% of UV penetrates overcast skies, and broken cloud edges can intensify UV by up to +25% through scattering reflections. Suntan Workout models this so you never get caught off-guard.
Yes, always. Suntan Workout manages timing and dosage to prevent acute erythema, but sunscreen shields your skin barrier and delicate areas (like lips, ears, and eyelids) from cumulative oxidative stress and photoaging.
100% free. There are no credit cards required, no automatic subscriptions, and no trial traps. You can download the app and use sessions 1 through 4 indefinitely with full live UV scaling.
Yes! The companion Apple Watch app mirrors your active session, displaying the current position and time remaining, and gently vibrates your wrist when it's time to rotate.
Erythema takes 6–12 hours to fully reveal itself. After each session, the app asks how your skin feels. If you answer 'Pink' or 'Burned', the app prevents you from progressing to higher rungs on the 12-step ladder, stepping you back safely to prevent compound burns.