The dental tooth numbering chart

The Universal Numbering System is the US standard. It numbers the 32 permanent teeth 1 through 32 in a single sweep, starting at the upper right third molar (1), across the top to the upper left third molar (16), down to the lower left third molar (17), and back to the lower right third molar (32).

Use the converter above, or the full chart below. Each FDI number encodes a quadrant (first digit) and a position from the midline (second digit), so FDI 46 is quadrant 4, position 6 — the lower right first molar — which is Universal 30. The quickest way to avoid errors is to look the tooth up rather than convert in your head.

FDI tooth 47 and Universal tooth 30 are different teeth. FDI 47 is the lower right second molar (Palmer LR7, Universal 31). Universal 30 is the lower right first molar (FDI 46, Palmer LR6). The two systems use overlapping numbers, which is exactly why converting carefully matters.

US dental practices use the Universal Numbering System (1-32). Insurance claims, dental education, and CDT coding in the United States are all built around it. Most of the rest of the world uses FDI (ISO 3950) two-digit notation.

Palmer notation identifies a tooth by its position 1-8 from the midline together with a quadrant symbol (or, in shorthand, a quadrant abbreviation such as UR, UL, LL, LR). It stays in some use among orthodontists and in the UK, though FDI has largely replaced it in digital records.