FDI
Two digits. First is the quadrant, 1–4 adult, 5–8 primary. Second is the position from the midline, 1–8 or 1–5. ISO 3950. The number a laboratory outside the United States expects.
Free converter · FDI · Universal · Palmer
#19 in the clinicis 36 in the lab.
Type 36. Read #19. Click LL6. The site does not move — only the notation. Free, in the browser, no account.
Clinic writes#19Universal · ADA
Laboratory reads36FDI · ISO 3950
Same site · three notations
Example TL–N19 · no patient data
FDI 11–85 · Universal 1–32 / A–T · Palmer UR1, LL6
Remake risk
A wrong number mills the wrong tooth.
Example case TL–N19, illustrative, no patient data. A US clinic writes Universal #19 — lower left first molar. A laboratory that works in FDI has no tooth 19. Production waits, or the mill starts on the wrong site.
This converter names the site in all three systems before anyone mills. The odontogram and Digital Rx pages show how a TrazaLab case is built to carry that same site onto the chart and the slip.
How they count
Three notations. One arch.
Universal
ADA 1–32 around the mouth, then A–T for primary teeth. Written with a hash on US slips. The number most US practice software still prints.
Palmer
A bracket for the quadrant — ┘ └ ┌ ┐ — and 1–8 from the midline. On a keyboard that becomes UR, UL, LL, LR. Still the shorthand on many UK and specialist charts.
Open the 32-site chart
Full register
Every permanent or primary site, side by side. Click a row to lock it on the chart.
| FDI · ISO 3950 | Universal · ADA | Palmer | Site | Quadrant |
|---|---|---|---|---|
| 18 | #1 | 8┘ · UR8 | Upper Right Third Molar (Wisdom Tooth) | Upper Right · Q1 |
| 17 | #2 | 7┘ · UR7 | Upper Right Second Molar | Upper Right · Q1 |
| 16 | #3 | 6┘ · UR6 | Upper Right First Molar | Upper Right · Q1 |
| 15 | #4 | 5┘ · UR5 | Upper Right Second Premolar | Upper Right · Q1 |
| 14 | #5 | 4┘ · UR4 | Upper Right First Premolar | Upper Right · Q1 |
| 13 | #6 | 3┘ · UR3 | Upper Right Canine (Cuspid) | Upper Right · Q1 |
| 12 | #7 | 2┘ · UR2 | Upper Right Lateral Incisor | Upper Right · Q1 |
| 11 | #8 | 1┘ · UR1 | Upper Right Central Incisor | Upper Right · Q1 |
| 21 | #9 | └1 · UL1 | Upper Left Central Incisor | Upper Left · Q2 |
| 22 | #10 | └2 · UL2 | Upper Left Lateral Incisor | Upper Left · Q2 |
| 23 | #11 | └3 · UL3 | Upper Left Canine (Cuspid) | Upper Left · Q2 |
| 24 | #12 | └4 · UL4 | Upper Left First Premolar | Upper Left · Q2 |
| 25 | #13 | └5 · UL5 | Upper Left Second Premolar | Upper Left · Q2 |
| 26 | #14 | └6 · UL6 | Upper Left First Molar | Upper Left · Q2 |
| 27 | #15 | └7 · UL7 | Upper Left Second Molar | Upper Left · Q2 |
| 28 | #16 | └8 · UL8 | Upper Left Third Molar (Wisdom Tooth) | Upper Left · Q2 |
| 38 | #17 | ┌8 · LL8 | Lower Left Third Molar (Wisdom Tooth) | Lower Left · Q3 |
| 37 | #18 | ┌7 · LL7 | Lower Left Second Molar | Lower Left · Q3 |
| 36 | #19 | ┌6 · LL6 | Lower Left First Molar | Lower Left · Q3 |
| 35 | #20 | ┌5 · LL5 | Lower Left Second Premolar | Lower Left · Q3 |
| 34 | #21 | ┌4 · LL4 | Lower Left First Premolar | Lower Left · Q3 |
| 33 | #22 | ┌3 · LL3 | Lower Left Canine (Cuspid) | Lower Left · Q3 |
| 32 | #23 | ┌2 · LL2 | Lower Left Lateral Incisor | Lower Left · Q3 |
| 31 | #24 | ┌1 · LL1 | Lower Left Central Incisor | Lower Left · Q3 |
| 41 | #25 | 1┐ · LR1 | Lower Right Central Incisor | Lower Right · Q4 |
| 42 | #26 | 2┐ · LR2 | Lower Right Lateral Incisor | Lower Right · Q4 |
| 43 | #27 | 3┐ · LR3 | Lower Right Canine (Cuspid) | Lower Right · Q4 |
| 44 | #28 | 4┐ · LR4 | Lower Right First Premolar | Lower Right · Q4 |
| 45 | #29 | 5┐ · LR5 | Lower Right Second Premolar | Lower Right · Q4 |
| 46 | #30 | 6┐ · LR6 | Lower Right First Molar | Lower Right · Q4 |
| 47 | #31 | 7┐ · LR7 | Lower Right Second Molar | Lower Right · Q4 |
| 48 | #32 | 8┐ · LR8 | Lower Right Third Molar (Wisdom Tooth) | Lower Right · Q4 |
Reference chart for clinic–laboratory communication. Confirm the site on examination and radiographs before design or milling. Example case TL–N19 is illustrative. No patient data.
The case continues
A number is not a prescription.
The converter settles the site. What follows is the rest of the order — findings, prescription, and the remake risk if the number still drifts.
Findings on the site
A number is a coordinate. The odontogram page shows how a chart holds conditions on that coordinate.
The slip carries the siteDigital Rx is the laboratory order. The site that left this converter has to be the site on that slip.
Wrong site is a remakeIf the mill starts on the wrong tooth, the work comes back. Remake prevention starts at the number.
Questions
The three systems, in writing
Which tooth numbering system is the international standard?
The FDI two-digit system (ISO 3950), designated by the World Health Organization and FDI World Dental Federation, is the official global standard. The first digit identifies the quadrant (1–4 for adult, 5–8 for primary), and the second digit indicates tooth position from midline (1–8 for adult, 1–5 for primary).
Why do dentists in the United States use the Universal system?
The Universal Numbering System was adopted by the American Dental Association (ADA) in 1968, shortly before the FDI standardized its two-digit system in 1970. US dental schools, practice software, and insurance forms were already built on 1–32 and A–T, so the national habit stayed.
How does Palmer notation work?
Palmer uses a grid bracket (┘, └, ┌, ┐) for the four quadrants as seen from the front. Each quadrant is numbered 1 through 8 from the midline to the third molar. In digital notes the brackets become UR, UL, LL, LR plus the number.
How does a numbering mismatch reach the mill?
When a clinic writes tooth #19 (lower left first molar in Universal) for a laboratory that works in FDI, the lab can read a number that does not exist in FDI or map it to the wrong tooth. Convert first. Then keep the same site name on the chart and the prescription.