# FDI to Universal tooth number converter

> Convert FDI / ISO 3950 two-digit tooth numbers to Universal and Palmer notation.

URL: https://dentovio.com/tools/fdi-to-universal-converter

Last verified: 2026-07-08

Neutral tooth-designation reference only; not clinical, diagnostic, or treatment advice.

## Direct answer

- FDI 18 is Universal 1, the upper right third molar.
- FDI 26 is Universal 14, the upper left first molar.
- FDI 36 is Universal 19, the lower left first molar.
- FDI 48 is Universal 32, the lower right third molar.
- Primary teeth use FDI quadrants 5-8 and Universal letters A-T.

## How FDI maps

The first FDI digit is the quadrant: 1 upper right, 2 upper left, 3 lower left, 4 lower right for permanent teeth. The second digit is the position from the midline, 1 for central incisor through 8 for third molar.

## Sources

- Source 1: American Dental Association — Universal Numbering System. <https://www.ada.org/publications/ada-news/2020/november/how-to-count-teeth-numbering-systems>
- Source 2: ISO 3950:2016 — Dentistry, designation system for teeth and areas of the oral cavity (FDI two-digit). <https://www.iso.org/standard/68292.html>
- Source 3: FDI World Dental Federation — two-digit notation. <https://www.fdiworlddental.org/>

## Related

- [Full tooth numbering chart](https://dentovio.com/tools/tooth-numbering-chart/index.html.md)
- [Palmer notation converter](https://dentovio.com/tools/palmer-notation-converter/index.html.md)