Every sleep app turns your night into one number using a recipe it invented. Tonight, you're the app. Below is one fixed night of sleep — it never changes. Mix your own recipe and watch its "score" swing.
Same night, every time. Only the recipe moves.
Slide the weights — how much should each ingredient count? (They're normalised to 100%.)
"Re-measure" re-estimates only the deep-sleep percentage — because stage estimates from consumer trackers are noisy, the number wobbles between measurements of the same night. Watch what it does to a stage-heavy score.
The three preset recipes are invented for this demo. They are not any real company's formula — real formulas are secret, which is rather the point.
You took one unchanging night and made it score anywhere from around 40 to the mid-90s by moving sliders. No sleep was harmed or improved. That is exactly what happens when the same night is scored by two different apps: different recipe, different number, same you.
And the "re-measure" button shows the second problem: some ingredients (stage estimates) are noisy guesses, so a recipe that leans on them produces a score that jumps around even when your sleep doesn't. If your score dropped seven points and you feel fine — this is usually why.
Two of the ingredients need no guessing and no recipe: total sleep time and efficiency. They come from asleep-versus-awake detection, which consumer trackers genuinely do well. Watch those two lines, compare yourself only to your own recent average, and let the headline number be entertainment. The full reasoning is in our guide: What is a good sleep score?
Rested is our free sleep app. It runs in your browser, keeps everything on your device, and labels honestly what is measured and what is only estimated.
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