If you wear a sleep tracker to bed, you have access to a mountain of data about your slumber. But, unless you understand the meaning behind the metrics, it can be difficult to translate those numbers into concrete strategies for better sleep.

Here are the most common metrics reported by sleep trackers, and how to use them to improve your slumber.

1. Sleep duration

Both the National Sleep Foundation and the American Academy of Sleep Medicine agree that adults need at least seven hours of sleep per night. To help you determine whether you meet this standard, sleep trackers report on your sleep duration.

To calculate this number, special sensors track your movement and heart rate throughout the night. If you're relatively still with a lower-than-normal resting heart rate, the device concludes you're asleep. If you're active and your resting heart rate remains normal, on the other hand, the device assumes you're awake.

Your sleep tracker is a smart device that learns over time. It benchmarks your norms, helping it to become more accurate as time passes. So, if your heart rate is typically lower than the average adult, your sleep tracker won't automatically assume you're asleep. Instead, it will wait until your heart rate drops from your daytime average.

How to lengthen your sleep

If you get less than seven hours of sleep per night, you may be sleep deprived. To get more shut-eye, follow these tips from the National Institutes of Health:

• Allow enough time for sleep. To get enough sleep, it's important to go to bed at least seven hours before you have to wake up.
• Keep a sleep schedule. If you go to bed at the same time each night, you'll have an easier time falling and staying asleep.
• Adhere to a bedtime routine. Turning off all electronics an hour before bed and practicing relaxation techniques to calm your body and mind can help you sleep. So, consider incorporating them into your bedtime routine.

2. Sleep stages

Most sleep trackers report how much time you spend in each sleep stage. Why? Because some stages affect your sleep quality more than others.

While asleep, our bodies and minds go through several stages of sleep, each with its own characteristics. This happens on repeat throughout the night.

Light sleep refers to stages 1 and 2 of non-REM sleep. During this stage, your muscles begin to relax, your body temperature falls, and your breathing, heart rate and eye movements slow. It's easiest to wake up during this stage, and some movement is not uncommon.

Deep sleep refers to stage 3 of non-REM sleep. In this stage, your body continues to relax. Your heart rate and breathing slow further. It's relatively hard to wake up during this stage.

Getting enough deep sleep helps you feel rested in the morning. Your mind and body perform several essential functions during deep sleep:

• Eliminating toxins from the brain.
• Consolidating new memories.
• Processing emotions.
• Recovering from physical strain.
• Strengthening your immune system.

REM sleep stands for rapid eye movement. During REM sleep, you sleep more deeply than in other stages, meaning it's very difficult to wake up. This is the stage when you dream. Like the name suggests, your eyes flutter and your breathing becomes sporadic. Fortunately, your muscles are in a state of paralysis, preventing you from moving around.

Sleep trackers can accurately identify sleep stages thanks to special sensors that measure heart rate variability.

How to get more deep sleep

While there's no minimum amount of light sleep to strive for, increasing your deep sleep can offer real health benefits. The American Sleep Association recommends three strategies for getting more deep sleep:

• Sleep longer. The easiest way to get more deep sleep is to sleep for longer periods of time. So, if you currently get six hours of sleep, strive for seven or eight.
• Exercise daily. Research suggests that vigorous exercise, such as running or swimming, leads to more deep sleep. Daily exercise also helps exhaust your body, signaling that it needs rest.
• Get warm. Heating your body throughout the day is shown to increase deep sleep. So, spend time in the sun, get more vigorous exercise, immerse yourself in a sauna or hot tub, take a hot bath before bed, and get cozy under a warm blanket.

3. Sleep quality

Your sleep tracker uses a proprietary algorithm, or set of rules, to make judgments about your sleep quality based on all the things it measures. When you're physically restless throughout the night with many times awake, the device assumes you slept poorly. When you get at least seven hours of undisturbed sleep, it assumes you slept well.

How to get a better quality sleep

If you wake up often or are frequently disturbed while sleeping, you may get a poor quality sleep. To avoid this, try these tips from the National Institutes of Health:

• Avoid stimulating substances before bed. Many substances can interfere with your ability to sleep, even if consumed hours before bedtime. Don't drink coffee after noon or eat large meals within a few hours of bedtime, and avoid consuming alcohol or cigarettes altogether, when possible.
• Control your sleep environment. Research shows that a room that's "quiet, cool, and dark" is most conducive to a good night's sleep. Do your best to limit disturbances by closing your curtains or blinds, keeping the window open, and using earplugs, if necessary.