IF YOU’RE ON the hunt for a good night’s sleep, you’re not alone: 40 percent of Americans get less than seven hours of sleep each night, and that’s well below the recommended eight hours of sleep your doctor’s always talking about. In fact, Americans average just 6.8 hours of sleep per night, so you’re in good company if you find yourself yawning uncontrollably by 2 p.m. at work.

Why Adequate Sleep Is Crucial

Unfortunately, if you regularly come in at a deficit where your sleep is concerned, you’re more likely to experience significant effects on your health. According to the National Institutes of Health (NIH), getting less than the recommended amount of sleep can cause all kinds of health problems, including:

• • Emotional distress
  • Learning issues
  • Heart disease
  • Kidney disease
  • High blood pressure
  • Obesity
  • Diabetes
  • Stroke
  • Accidents

And if you’re worried about your own sleep patterns, imagine how much harder it is for kids to get up — sometimes before dawn! — and be ready to do their best in school. Because their bodies are expending so much energy on growing and developing, they need even more sleep than adults.

But they often don’t get it, especially as American families are prone to over-scheduling and under-relaxing these days.

Recommended Hours of Sleep by Age

So how much sleep do you really need? And how is that different from what your child needs or what your grandma needs?

Though there are individual variations, the National Sleep Foundation has 25 years of research on the subject. Here are their recommendations:

• • Newborns — Age 0-3 months: 14 to 17 hours per day. Less than 11 is not enough.

• • Infants — Age 4-11 months: 12 to 15 hours per day. Less than 10 is not enough.

• • Toddlers — Age 1-2 years: 11-14 hours per day. Less than 9 hours is not enough.

• • Preschoolers — Age 3-5 years: 10-13 hours per day. Less than 8 hours is not enough.

• • School Age Children — Age 6-13 years: 9-11 hours per day. Less than 7 hours is not enough.

• • Teenagers — Age 14-17 years: 8-10 hours per day. Less than 7 hours is not enough.

• • Adults — Age 18-64 years: 7- 9 hours per day. Less than 6 hours is not enough.

• • Older Adults — Age 65+ years: 7-8 hours per day. Less than 5 hours is not enough.

As adults age, they gradually need less sleep. It may be common for younger adults between the ages to 18-25 to be on the high end of the scale, requiring nine hours for good health, while the average adult between the age of 26 and 65 need closer to the standard eight hours of sleep you hear so much about.

The irony? When you reach retirement age, you’ll probably get more sleep, but you won’t actually need as much.

How to Calculate Your Ideal Bedtime

Though figuring out your bedtime is a problem with an obvious solution, you may be surprised once you actually sit down and do the math. All you have to do is check your age recommendation and count backwards from the time you need to be up in the morning to get your recommended bedtime.

Is it earlier than you thought? Many people find that they should be heading to bed well before the 11 o’clock news. If this seems difficult, try streamlining your morning routine and turning off the TV and computer at least an hour before your new bedtime so you won’t feel like you’re missing out on anything.