← Back to Tools

Sunlight Window Calculator

Huberman says morning sunlight is non-negotiable. But how long do you actually need to stand outside? Calculate your minimum effective dose based on today's weather.

Recommended Duration

10 Minutes

Get outside within 1 hour of waking. Do not wear sunglasses. Do not look directly at the sun. Window glass filters out the required wavelengths, so you must be outside.

Lost track of time?

The ARC app features a live, active Sunlight Timer. It uses your local weather API to calculate the exact lux and counts down the minutes in your ear while you walk.

Get ARC Pro

The Science of Light Viewing

Light is the primary driver of your circadian rhythm. When photons hit your eyes, they stimulate specialized cells called ipRGCs (intrinsically photosensitive retinal ganglion cells). These cells don't help you see shapes; they detect the presence of blue-wavelength light and tell your brain what time of day it is.

According to neurobiologists like Dr. Andrew Huberman, getting bright light in your eyes within an hour of waking is the single most important habit for sleep, mood, and energy.

Why Does Weather Matter?

The intensity of light is measured in lux. On a clear, sunny day, looking toward the sky (not directly at the sun) provides roughly 10,000 to 50,000 lux. On a heavy overcast day, that intensity drops to about 1,000 lux.

Your brain needs a certain cumulative threshold of photons to trigger the cortisol spike and stop melatonin production. If it's cloudy, you simply need to stand outside longer to get the same biological effect.

Rules for Light Viewing

  1. Be Outside: Window glass filters out the blue light wavelengths required to reset your clock. You must be outdoors.
  2. No Sunglasses: Sunglasses block the light your brain needs. Clear prescription glasses or contacts are perfectly fine.
  3. Do Not Stare at the Sun: Look toward the sky, but never directly at the sun to avoid retinal damage.

We're here to help.

Need help understanding the science? Or is the subscription price a bit too high for you right now? Let's chat.

DM on X (@iPritamX)DM on Insta (@arc.sync)Email Support
Got questions? Let's chat 👋