Most adults have 12 molars: three in each corner of the mouth, for a total of six on top and six on the bottom. That count includes your four wisdom teeth (third molars), which not everyone develops. If your wisdom teeth never came in or were removed, you may have as few as eight molars.
Where Your 12 Molars Sit
Your molars are the wide, flat teeth at the very back of your mouth. Dentists divide the mouth into four quadrants (upper right, upper left, lower right, lower left), and each quadrant holds three molars. From front to back, they’re called the first molar, second molar, and third molar (wisdom tooth).
Adults have 32 permanent teeth in total: 8 incisors, 4 canines, 8 premolars, and 12 molars. Molars make up more than a third of your teeth, and roughly 90% of your chewing happens on them.
Premolars vs. Molars
A common source of confusion is the difference between premolars and molars. Premolars (sometimes called bicuspids) sit just in front of the molars, between your canines and the back of your mouth. Adults have 8 premolars. They look somewhat similar to molars but are smaller, with only two cusps on top instead of three to five. Premolars help tear and crush food, while molars handle the heavy grinding.
How Molars Differ From Top to Bottom
Upper and lower molars are built differently. Upper molars have three roots (two on the cheek side and one longer root on the tongue side) and typically four cusps on their biting surface. Some upper molars also have a small extra bump on the tongue side called a Carabelli cusp. Lower molars have just two roots but tend to be wider. The lower first molar is actually the widest tooth in your entire mouth, with a five-sided biting surface and five cusps.
That extra width matters. Measurements of bite force show that the back teeth can generate around 440 newtons of pressure, roughly three times the force your canines and premolars produce. Molars are built to handle that load.
When Each Molar Comes In
Molars arrive in three waves. First molars erupt between ages 6 and 7, which is why they’re sometimes called “six-year molars.” These are the first permanent teeth that don’t replace a baby tooth; they emerge behind the existing baby molars. Second molars follow between ages 11 and 13. Third molars (wisdom teeth) are the last to appear, typically between 17 and 21, if they come in at all.
Children have their own set of molars before the permanent ones arrive. The primary (baby) set includes 8 molars: 4 on top and 4 on the bottom. The first baby molars show up around 13 to 19 months, and the second baby molars come in around 23 to 33 months. These are eventually replaced by the 8 adult premolars, not by adult molars. The permanent first, second, and third molars grow in behind the spot where the baby molars sat.
Why You Might Have Fewer Than 12
Plenty of adults have fewer than 12 molars, and the most common reason is wisdom teeth. About one in three people are born without one or more third molars. The teeth simply never develop in the jawbone. Third molars are the most frequently missing teeth in the human mouth, a trend many researchers attribute to evolutionary changes in jaw size.
Even when wisdom teeth do develop, they often don’t come in cleanly. Studies using panoramic X-rays find that roughly 34% of people have at least one impacted wisdom tooth, meaning it’s stuck below the gum line or growing at an angle. Impacted or partially erupted wisdom teeth are one of the most common reasons for dental extraction, which is why many adults end up with 8 molars instead of 12.
Less commonly, a first or second molar may be lost to severe decay or gum disease. Because these teeth bear so much chewing force, dentists typically recommend replacing a lost first or second molar with a crown, bridge, or implant to keep bite alignment stable.
How to Count Your Own Molars
Run your tongue along the back of your mouth behind your premolars. Each molar feels noticeably wider and bumpier than the teeth in front of it. In each quadrant, count backward from the last premolar. If you feel three large, bumpy teeth, you have all three molars on that side. If you only feel two, your wisdom tooth on that side either never developed, hasn’t erupted yet, or was removed. Add up all four quadrants for your total.