Wellness
Bedtime from a wake time
Count back whole cycles plus the time to fall asleep, so the alarm lands at the end of a cycle rather than in the middle.
The Formula
bedtime = wake - 15 - 90 x cycles
Count back whole cycles plus the time to fall asleep, so the alarm lands at the end of a cycle rather than in the middle.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| t_bed | Bedtime | clock time | When to get into bed. |
| t_wake | Wake time | clock time | When the alarm is set. |
| n | Cycles | cycles | Number of 90 minute cycles, usually four to six. |
What Each Symbol Means
t_bedclock time
Bedtime
When to get into bed.
t_wakeclock time
Wake time
When the alarm is set.
ncycles
Cycles
Number of 90 minute cycles, usually four to six.
See It Worked With Real Numbers
A formula on its own does not tell you which number goes where. The how to calculate the best time to sleep page applies this equation to a concrete case, shows every intermediate step, and names the mistakes that produce a wrong answer even when the algebra is right.
Where This Formula Appears
This equation is the working core of How To Calculate The Best Time To Sleep, filed under Health. Every number the guide produces comes from substituting into this one line.