RISE calculates your sleep debt by comparing the amount of sleep you actually got to the amount of sleep you needed over the past 14 nights. If you slept less than your sleep need on any of those nights, the difference adds to your sleep debt. If you slept more, it helps pay that debt back down.
RISE uses two inputs: your personal sleep need and how much you slept each night.
Your sleep need is the amount of sleep your body requires to function at its best. RISE estimates your sleep need by analyzing up to 365 nights of your sleep data, looking for patterns of sleep rebound — periods when you sleep longer than usual after stretches of shorter sleep. These rebounds reveal your true biological need. RISE also applies upper and lower limits based on peer-reviewed research, so your estimate won't be unrealistically high or low even if you've been chronically under-sleeping. You can manually adjust your sleep need if it seems too high or too low — see How do I manually adjust my sleep need? (#6) for steps.
Your sleep data comes from whichever tracking method RISE is using — whether that's phone-based (phone motion), mattress-based (mattress detection), or a connected third-party wearable.
Each morning, RISE compares these two numbers. If you consistently fall short of your sleep need, the gaps accumulate into sleep debt. If you get more sleep than you need, it helps bring that debt back down.
Why does RISE use 14 nights?
RISE calculates sleep debt over a rolling 14-night window because research shows that accumulated sleep loss over roughly two weeks is what drives how you feel and perform on any given day. One short night matters, but so do the 13 nights before it.
RISE also weights recent nights more heavily than older ones. A night where you didn't meet your sleep need two days ago has more impact on your current sleep debt than the same shortfall twelve days ago. This means your sleep debt number reflects both your recent sleep and your longer-term pattern, without treating every night equally.
What is a good sleep debt number?
RISE recommends keeping your sleep debt under five hours to feel and function your best. A sleep debt of zero is ideal but not always realistic — the goal is to keep the number as low as you can.
The best ways to pay down your sleep debt are to go to bed a little earlier, sleep a little later, or take naps, which count toward paying down your sleep debt. Improving your sleep habits also helps — they can help you fall asleep faster and stay asleep longer, which means more sleep per night.
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