Sleep Duration Calculator
Enter your bedtime and wake time to see exactly how much you slept — and how many 90-minute cycles you completed.
Sleep Duration Calculator
Enter your bedtime and wake time to see total sleep, completed cycles, and a quality rating.
How the sleep duration calculator works
A sleep duration calculator turns two numbers — when you went to bed and when you got up — into something useful. We work out total time in bed, subtract about 15 minutes to fall asleep, and divide the rest by 90 minutes to count your completed sleep cycles.
If you have wondered “how much sleep did I get?” the honest answer is not just the clock difference. It is how many full cycles fit in that window. Five complete cycles (about 7.5 hours) is a common sweet spot; four or more is solid; fewer than three is usually short for most adults.
Why count cycles, not just hours?
Hours tell you how long you were in bed. Cycles tell you whether you actually rested. Waking mid-cycle — during deep sleep — leaves you groggy even after a long night. The 90-minute model used here is grounded in sleep science, including the National Sleep Foundation's duration guidance (2022), and it is the same model behind every Restcalc tool.
A few quick tips
- Aim for 4–6 full cycles rather than a fixed hour count.
- If quality reads low, try 30–60 minutes more in bed.
- Track a few nights with the Sleep Log to see your pattern.
Frequently asked questions about the Sleep Duration Calculator
Everything you need to read your results confidently.
Explore more sleep tools
Each one plans sleep around your 90-minute cycles.