Depending on where you trained, the upper right first molar might be "16", "3", or just "upper right first molar". All three are correct, and all three get you the same tooth from us. Every tooth on our site is listed in FDI, ADA and plain English, and our team works in both systems every day. If you can describe the tooth, we can find it.

One tooth, three names

Take the big molar at the back of the upper right side of the mouth, the upper right first molar.

Same tooth. The systems just count differently.

How FDI works: quadrant, then tooth

FDI uses two digits, and they are read separately, so 16 is "one-six", not "sixteen".

The first digit is the quadrant, going clockwise as you face the patient: 1 is upper right, 2 is upper left, 3 is lower left and 4 is lower right.

The second digit counts back from the middle of the mouth: 1 is the central incisor and 8 is the wisdom tooth.

So 16 means upper right (1), sixth tooth back (6): the first molar. Once you know that, 36 is easy. Lower left, sixth tooth back: the lower left first molar.

How ADA works: one long count

ADA (also called the Universal system) numbers the teeth 1 to 32 in a single loop. Start at the upper right wisdom tooth as 1, count across the top to the upper left wisdom tooth at 16, drop down to the lower left wisdom tooth at 17, and count back across the bottom to the lower right wisdom tooth at 32.

So ADA 3 is the third tooth in from the upper right: the first molar again.

The full chart

Find your tooth by name, then read across for its number in either system.

Baby teeth

Primary teeth follow the same logic with different labels. FDI uses quadrants 5 to 8, so the upper right primary second molar is 55. ADA uses letters A to T in the same loop, starting with A at the upper right primary second molar.