SolarDose
2026 · solardose.appWhen should you actually step outside to make vitamin D? SolarDose computes your personal sun-exposure window — from location, date, skin type, weather and altitude.
Nearly half the world is vitamin-D insufficient, yet the fix is simple: a few minutes of sun — at the right time. The catch is that skin only synthesizes vitamin D when the sun climbs above ~35°, so most early-morning and late-evening sun does nothing.
SolarDose runs SunCalc.js to compute the sun's elevation minute-by-minute, marks the synthesis window, then personalizes the dose using the Fitzpatrick skin scale, the Holick rule, exposed body area, real-time cloud cover (Open-Meteo) and altitude. The hardest problem was timezone correctness — solved by anchoring every calculation to the location's true UTC offset.
Unlike the incumbents — one clunky and manual, one $20/year with battery-draining tracking — SolarDose is free, registration-free and open source, with 50 SEO landing pages (25 cities × TR/EN) for organic reach.