Are wake windows exact?

No. They are a rule of thumb, not clinical guidance. Babies differ, so use the range as a prompt to start watching for tired cues rather than a fixed alarm.

Does this calculator send my data anywhere?

No. It runs entirely in your browser. Nothing you enter is uploaded or stored on a server.

How do I use this with twins?

Work out each twin's window, then aim to overlap them by matching wake times. Tracking both babies' wake times is what keeps the naps lining up.

Wake window calculator: when is the next nap?

Wake window calculator

Baby's age

Last woke at

Everything is worked out in your browser. Nothing you enter is sent anywhere.

What a wake window is

A wake window is how long a baby can comfortably stay awake between sleeps before they get overtired. It grows with age, which is why a nap time that worked last month drifts this month. The calculator adds a typical window for the age band you pick to the time your baby last woke.

How reliable is this?

Treat the result as a starting point, not an alarm. Wake windows are a popular rule of thumb rather than medical guidance, and every baby is different. Tired cues, such as yawning, staring or getting fussy, beat the clock. If your baby is consistently fighting sleep at the suggested time, shift the window a little and watch what settles them.

Using it with twins

Run each twin through the calculator, then aim to overlap their naps by nudging their wake times together. That overlap is where your break comes from, and tracking both babies' wake times is what makes it repeatable.

Quick answer

This wake window calculator gives you a rough time range for the next nap: pick your baby's age band and enter when they last woke, and it adds an age-appropriate wake window. It runs entirely in your browser, and nothing you enter is sent anywhere. Wake windows are a guide, not a rule, so pair the result with your baby's tired cues.

How to use it

Pick the age band. Choose the range that matches your baby's age; each band uses a typical wake window for that age.
Enter the last wake time. Set the time your baby last woke from sleep. The calculator fills in the current time to start with.
Read the nap window. The result shows the range to aim for the next nap, so start winding down toward the earlier end if you see tired cues.

Frequently asked questions

Are wake windows exact?: No. They are a rule of thumb, not clinical guidance. Babies differ, so use the range as a prompt to start watching for tired cues rather than a fixed alarm.
Does this calculator send my data anywhere?: No. It runs entirely in your browser. Nothing you enter is uploaded or stored on a server.
How do I use this with twins?: Work out each twin's window, then aim to overlap them by matching wake times. Tracking both babies' wake times is what keeps the naps lining up.