Most adults sleep best on their side, in a cool room (60 to 67°F), for 7 to 9 hours per night. But the ideal way to sleep depends on your body, your health, and a few habits that happen hours before you ever get into bed. Here’s what actually matters.
The Best Sleep Position for Most People
Side sleeping is generally the strongest default choice. It keeps your airway open by preventing the tongue and soft tissues at the back of the throat from collapsing, which reduces snoring and helps with sleep apnea. If you deal with acid reflux, the left side is especially helpful: it positions your esophagus above your stomach, making it harder for acid to travel upward. A meta-analysis of clinical studies found that left-side sleepers had significantly fewer reflux episodes per hour and faster acid clearance compared to people sleeping on their back or right side.
The tradeoff with side sleeping is pressure. Your shoulder, hip, and neck absorb more of your body weight, which can create soreness, especially if you already have joint issues. A pillow between your knees helps keep your hips aligned and takes stress off your lower back.
When Back Sleeping Works Better
If you have neck, back, or hip pain and don’t snore, sleeping on your back distributes your weight more evenly and removes sideways force from the spine. Many people wake up with less morning stiffness in this position. The catch is that gravity pulls all the soft tissue in the back of your throat downward, which narrows the airway. For snorers and people with sleep apnea, this position reliably worsens symptoms. Research confirms that airway obstruction occurs more frequently on your back, particularly at the level of the soft palate and epiglottis.
Back sleeping also makes acid reflux worse and can feel like pressure on the chest for people carrying extra weight in their midsection or those with heart or lung conditions. If you’re pregnant, the American College of Obstetricians and Gynecologists recommends avoiding back sleeping after the first trimester because the weight of the fetus can compress major blood vessels.
Why Stomach Sleeping Is the Least Ideal
Sleeping on your stomach forces your neck into a turned position for hours and flattens the natural curve of your spine. It’s not recommended for most people. If it’s the only position you can fall asleep in, a very thin pillow (or no pillow at all) under your head and a flat pillow under your pelvis can reduce some of the strain.
How Your Pillow Height Matters
Your pillow should fill the gap between your head and the mattress without tilting your neck up or letting it sag down. The right height depends entirely on your position. Research on pillow ergonomics suggests that back sleepers do well with a pillow around 7 to 10 centimeters (roughly 3 to 4 inches), while side sleepers need something higher, closer to 10 centimeters or more, to keep the head level with the spine.
If you switch between side and back sleeping during the night, contoured pillows that are lower in the center and higher on the sides can accommodate both. The key test is simple: your neck should feel like a natural extension of your spine, not angled in either direction.
Set Your Room Temperature to 60–67°F
Your body needs to drop its core temperature slightly to initiate deep sleep. A bedroom between 60 and 67°F (15 to 19°C) supports this process. If the room is too warm, you’re more likely to wake during the night or spend less time in the deeper, more restorative stages of sleep. For babies and toddlers, the sweet spot is a bit higher, between 65 and 70°F.
Light and Screens Before Bed
Your brain’s sleep hormone is highly sensitive to light, especially blue-wavelength light from phones, tablets, and laptops. Even low levels of blue light can disrupt its production. The suppression effect is most significant during the 30 to 90 minutes before sleep, which is exactly when most people are scrolling in bed. Dimming overhead lights and putting screens away at least 30 minutes before bed gives your brain a meaningful head start on producing the hormones that make you drowsy.
The flip side of this sensitivity works in your favor in the morning. Getting sunlight before 10 a.m. helps anchor your internal clock. A study in BMC Public Health found that every additional 30 minutes of morning sun exposure shifted people’s sleep timing earlier by about 23 minutes and improved their overall sleep quality scores. You don’t need special equipment. A morning walk, coffee on the porch, or even sitting near a bright window counts.
When to Stop Eating and Drinking Caffeine
Eating a full meal too close to bedtime disrupts more than just comfort. A clinical trial comparing dinner at 6 p.m. versus 10 p.m. (with sleep at 11 p.m.) found that the late meal caused significantly higher blood sugar during the night, delayed fat processing, and reduced the body’s ability to burn dietary fat. Finishing your last substantial meal at least 3 hours before bed gives your body time to handle digestion before sleep takes over.
Caffeine lasts longer in your system than most people realize. A systematic review and meta-analysis calculated that a standard cup of coffee (about 107 mg of caffeine) should be consumed at least 8.8 hours before bedtime to avoid reducing total sleep time. For higher-caffeine drinks like pre-workout supplements (around 217 mg), the cutoff extends to over 13 hours. If you go to bed at 11 p.m., that means your last regular coffee should be around 2 p.m. at the latest.
Alcohol Isn’t a Sleep Aid
Alcohol might help you fall asleep faster, but it fragments the second half of the night. It suppresses the deeper, dream-rich stages of sleep your brain needs for memory consolidation and emotional regulation. Even moderate amounts in the evening lead to more nighttime awakenings and lighter sleep overall. If you drink, earlier in the evening is better than closer to bed.
Position Tips for Specific Conditions
- Acid reflux or GERD: Sleep on your left side. If possible, elevate the head of your bed by a few inches using a wedge or bed risers, rather than stacking pillows (which can bend your neck without actually elevating your torso).
- Snoring or sleep apnea: Avoid sleeping on your back. Side sleeping keeps the airway more open. Vibrotactile devices worn on the neck or chest can gently prompt you to roll off your back during the night, and clinical trials support their effectiveness.
- Lower back pain: Back sleepers can place a pillow under the knees to maintain the spine’s natural curve. Side sleepers benefit from a pillow between the knees.
- Pregnancy (second and third trimesters): Left-side sleeping promotes blood flow to the uterus and reduces swelling in the legs and ankles. Avoid sleeping flat on your back.
- Shoulder pain: Sleep on the opposite side, or switch to back sleeping until the shoulder heals.
How Many Hours You Actually Need
Adults between 18 and 64 need 7 to 9 hours of sleep per night. Adults over 65 do well with 7 to 8 hours. These aren’t aspirational numbers. Consistently sleeping below 7 hours is linked to impaired concentration, weakened immune function, and higher risks of chronic disease. The right amount for you is the number of hours that lets you wake up without an alarm and feel alert within about 20 minutes of getting out of bed.