If you've ever tried to demystify your little one's sleep cycle so that you can figure why he or she wakes up at the drop of a pin at some times yet can sleep through a car alarm at others, this nifty little downloadable widget may help you get to the bottom of things.

Lisa at Infinite Monkey Theory and Joel of Made by Joel teamed up to create this free mini-application, which works like this:

The Sleep Cycle Calculator is based on the premise that babies and children sleep in 40 to 45 minute cycles. To use the calculator, all you have to do is input the start time for your child's nap, and the calculator will tell you when each sleep cycle will end – meaning you should be extra quiet because that's when they'll be sleeping the most lightly. You can also customize the sleep cycle length if you deduce that your child's sleep cycles are longer or shorter than average.

Curious? Skeptical? Desperate? Download the calculator here and give it a run for yourself.