RayDay vs BigDose
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
RayDay
This app calculates your daily window for natural Vitamin D production based on your location and skin type. It provides solar path visualization, forecasts, and atmospheric data to help you optimize sun exposure safely.
- D-Window Calculator
- Live Solar Path visualization
- 7-Day D-Window Forecast
- Skin Type Personalization
- Smart Sun Exposure Notifications
- Real-time UV Index & Atmospheric Data
- Home Screen Widget
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I built RayDay after years of working indoors left me Vitamin D deficient. The fix wasn't another bottle of pills. It was knowing exactly when the sun was high enough so my body could make Vitamin D the way it always has: naturally, on its own. That's all RayDay does: it tells you your daily sun window, personalized to where you live and your skin type, so you can get Vitamin D the way your body was built to. FEATURES: • D-Window Calculator: know exactly when Vitamin D production is possible today and tomorrow • Live Solar Path: a beautiful animated arc showing the sun's position, sunrise, sunset, and the highlighted D-Window • 7-Day Forecast: see your D-Window for the coming week • Skin Type Personalization: your Fitzpatrick type determines how fast you make Vitamin D • Smart Notifications: get alerted before optimal sun days, plus a heads-up when winter's first D-Window returns • Atmospheric Data: real-time UV index, cloud cover, humidity, and altitude • Phase-Aware Design: app colors shift with the time of day. Dawn, daytime, sunset, and night • Home Screen Widget: a quick glance at your D-Window status • Works Worldwide: accurate for any latitude, including polar regions HOW IT WORKS: RayDay uses NOAA solar position algorithms to calculate the sun's altitude throughout the day. When the sun crosses 35° above the horizon, UVB rays penetrate the atmosphere. That's your D-Window for Vitamin D synthesis. The app factors in your Fitzpatrick skin type to recommend exposure durations that hit your daily IU goal without overexposure. Some features require a paid subscription. DISCLAIMER: RayDay is for educational purposes only. Consult a healthcare professional before changing Vitamin D supplementation or sun exposure habits. --- LEGAL: Privacy Policy: http://www.jakubl.com/privacy.html Terms of Use (EULA): http://www.jakubl.com/terms.html SUPPORT: support@jakubl.com X: @jakublaszczyk
BigDose
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Most sun apps pick a lane: vitamin D or sun safety. BigDose tracks both — in real time — so you can get outside with a plan instead of a guess. DOSE YOUR D. DEFEND YOUR SKIN. BigDose is built for people who want vitamin D from the sun and still respect their skin. We combine live Apple Weather, your skin type, sunscreen habits and sun angle to show when conditions are right for UVB — and when burn risk is climbing. YOUR DAILY COMMAND CENTER • Vitamin D window today — a sun-path diagram with Apple Weather sunrise and sunset, your personal D window, total daylight and how today compares to yesterday • Live UV, humidity, cloud cover, hourly and 3-day forecast from WeatherKit at your GPS • Daily sun IU goal with progress from sessions, supplements and food logged separately — no double-counting • Sun risk today when live sessions push past your personal burn threshold • Recommended daily IU tuned to age, skin type and goals LIVE SUN SESSIONS THAT RESPECT BOTH GOALS Start a session when your window is open. BigDose tracks elapsed time, estimated vitamin D toward your daily target and MED (burn risk) used on a live dial. Alerts when session safety is on: • Turn-over near 50% — rotate exposure • Optional Nanny Mode adds wrap-up at 75%, guidance at 95% and a 98% reminder • Stop-now at 100% MED — always, Nanny on or off You always end the session. We never do it for you. DOSE DNA — YOUR PROFILE, YOUR MATH Set Fitzpatrick skin type, typical coverage, sunscreen use, supplement defaults and a blood-level goal in ng/mL. BigDose personalizes session timing, safe max duration and safety alerts to you — not a generic chart. PLAN BEFORE YOU STEP OUTSIDE Session planner shows safe max duration at today’s UV, time to reach your D goal and milestone timeline. First-session guide walks new users through the dial, alerts and how to stop on their terms. PROGRESS THAT CONNECTS INTAKE TO LEVEL Log supplements and vitamin D food sources. Import labs when you have them. Progress estimates how your 25(OH)D trend is moving toward your goal using sun, pills and diet — with honest limits: modeled estimates, not a lab result. History keeps a ledger of sun, supplements and food by day. NOTIFICATIONS THAT MATCH YOUR STYLE Solar event reminders, next D opportunity nudges, optional AM light window alerts and session safety notifications when the app is in the background. Toggle what you want during onboarding or anytime in Settings. Nanny defaults on — turn it off when you want a lighter touch. SMART GUIDANCE, NOT A LECTURE Science tab explains how BigDose thinks about D and burn risk in plain language. Info buttons throughout — tap the (i) when you want context, skip them when you do not. BUILT FOR REAL OUTDOOR DAYS Live Activities keep an active session on your Lock Screen. Home Screen widgets surface today’s plan. Optional Apple Health import. High-contrast UI designed for glare, gloves and one-handed use outside. WHAT BIGDOSE IS — AND IS NOT BigDose is wellness guidance you choose to use. It is not medical advice, not a diagnosis and not a substitute for your clinician. Blood tests remain the source of truth for vitamin D status. Use shade, clothing and sunscreen beyond what any app can model. Whether you are optimizing morning light, chasing a short mid-day window or logging a supplement on a rainy day, BigDose helps you dose your D and defend your skin — same app, same dashboard, no false tradeoff. We ship often and read every report. Thanks for helping us make BigDose sharper every build.
Screenshots
Verdict
The clearest difference is in-app purchases: BigDose at none against RayDay's 3. BigDose also leads on update cadence (every 2 days vs every 3 weeks). RayDay's advantage is iOS requirement (17.0 vs 26.0). On price, ads and device support there is nothing between them.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
Both are free to download. RayDay sells 3 in-app purchases, starting at $4.99 per 7 days. BigDose asks for nothing beyond the download.
RayDay ships an update every 3 weeks, BigDose every 2 days. The most recent releases landed on October 17, 2026 and October 16, 2026 respectively.
| Parameter | RayDay | BigDose |
|---|---|---|
| Price | Free | Free |
| Rating | 3.0 (2 ratings) — better | — |
| Number of ratings | 2 — better | — |
| Update frequency | Every 3 weeks | Every 2 days — better |
| Ads | No | No |
| In-app purchases | Yes | No — better |
| Monetization | Free | — |
| Devices | iPhone, iPad | iPhone, iPad |
| Requires iOS | 17.0 — better | 26.0 |
| Further details — not scored | ||
| Size | 28 MB | 10 MB |
| Age rating | 4+ | 4+ |
| Developer | Jakub Laszczyk | Grant Perry |
In-app purchases
RayDay
- RayDay Weekly3 Days trial$4.997 Days
- RayDay Yearly$24.991 Year
- Early Supporter Yearly1 Year trial$24.991 Year
BigDose
No in-app purchases









