Tap a tooth or search a number to convert between the U.S. Universal system and the FDI/ISO two-digit system commonly encountered in Canada and internationally.
Quick answer: The Universal system numbers permanent teeth 1–32 and baby teeth A–T. The FDI/ISO system uses two digits: the first is the quadrant and the second is the tooth's position from the centre of the mouth. For example, Universal #19 is FDI 36, the lower-left first molar.
Updated: November 12, 2026
Your treatment plan says “tooth #19.” That is the Universal number. Count from the upper-right wisdom tooth (#1) across the top to #16, then drop to the lower-left wisdom tooth (#17) and continue: #19 is the lower-left first molar.
In FDI/ISO the same tooth is 36: quadrant 3 (lower left) and position 6 (first molar). In Palmer notation it is LL6. Three labels, one tooth.
Right and left always mean the patient's right and left. Palmer notation is shown as text (UR = upper right, UL = upper left, LL = lower left, LR = lower right) followed by the position from the midline.
| Universal | FDI / ISO | Palmer | Tooth name | Location |
|---|---|---|---|---|
| #1 | 18 | UR8 | Third molar (wisdom tooth) | Upper right |
| #2 | 17 | UR7 | Second molar | Upper right |
| #3 | 16 | UR6 | First molar | Upper right |
| #4 | 15 | UR5 | Second premolar | Upper right |
| #5 | 14 | UR4 | First premolar | Upper right |
| #6 | 13 | UR3 | Canine (cuspid) | Upper right |
| #7 | 12 | UR2 | Lateral incisor | Upper right |
| #8 | 11 | UR1 | Central incisor | Upper right |
| #9 | 21 | UL1 | Central incisor | Upper left |
| #10 | 22 | UL2 | Lateral incisor | Upper left |
| #11 | 23 | UL3 | Canine (cuspid) | Upper left |
| #12 | 24 | UL4 | First premolar | Upper left |
| #13 | 25 | UL5 | Second premolar | Upper left |
| #14 | 26 | UL6 | First molar | Upper left |
| #15 | 27 | UL7 | Second molar | Upper left |
| #16 | 28 | UL8 | Third molar (wisdom tooth) | Upper left |
| #17 | 38 | LL8 | Third molar (wisdom tooth) | Lower left |
| #18 | 37 | LL7 | Second molar | Lower left |
| #19 | 36 | LL6 | First molar | Lower left |
| #20 | 35 | LL5 | Second premolar | Lower left |
| #21 | 34 | LL4 | First premolar | Lower left |
| #22 | 33 | LL3 | Canine (cuspid) | Lower left |
| #23 | 32 | LL2 | Lateral incisor | Lower left |
| #24 | 31 | LL1 | Central incisor | Lower left |
| #25 | 41 | LR1 | Central incisor | Lower right |
| #26 | 42 | LR2 | Lateral incisor | Lower right |
| #27 | 43 | LR3 | Canine (cuspid) | Lower right |
| #28 | 44 | LR4 | First premolar | Lower right |
| #29 | 45 | LR5 | Second premolar | Lower right |
| #30 | 46 | LR6 | First molar | Lower right |
| #31 | 47 | LR7 | Second molar | Lower right |
| #32 | 48 | LR8 | Third molar (wisdom tooth) | Lower right |
Children have 20 primary teeth. Palmer notation uses letters A–E for baby teeth, counted from the midline.
| Universal | FDI / ISO | Palmer | Tooth name | Location |
|---|---|---|---|---|
| A | 55 | URE | Second molar | Upper right |
| B | 54 | URD | First molar | Upper right |
| C | 53 | URC | Canine (cuspid) | Upper right |
| D | 52 | URB | Lateral incisor | Upper right |
| E | 51 | URA | Central incisor | Upper right |
| F | 61 | ULA | Central incisor | Upper left |
| G | 62 | ULB | Lateral incisor | Upper left |
| H | 63 | ULC | Canine (cuspid) | Upper left |
| I | 64 | ULD | First molar | Upper left |
| J | 65 | ULE | Second molar | Upper left |
| K | 75 | LLE | Second molar | Lower left |
| L | 74 | LLD | First molar | Lower left |
| M | 73 | LLC | Canine (cuspid) | Lower left |
| N | 72 | LLB | Lateral incisor | Lower left |
| O | 71 | LLA | Central incisor | Lower left |
| P | 81 | LRA | Central incisor | Lower right |
| Q | 82 | LRB | Lateral incisor | Lower right |
| R | 83 | LRC | Canine (cuspid) | Lower right |
| S | 84 | LRD | First molar | Lower right |
| T | 85 | LRE | Second molar | Lower right |
Dentists use tooth numbers to identify a specific tooth in charts, treatment plans, referrals, insurance records, and clinical notes. The same tooth can carry a different label depending on the system.
In the Universal system, permanent teeth run from 1 to 32. The sequence starts at the patient's upper-right third molar, crosses the upper arch, then continues from the lower-left third molar across the lower arch.
In FDI/ISO notation, permanent quadrants are 1 to 4 and primary quadrants are 5 to 8. The second digit counts outward from the centre of the mouth.
| Feature | Universal / National | FDI / ISO | Palmer |
|---|---|---|---|
| Permanent teeth | 1–32 | 11–48 | 1–8 in each quadrant |
| Primary teeth | A–T | 51–85 | A–E in each quadrant |
| Structure | One running sequence | Quadrant digit + position digit | Quadrant symbol + position |
| Where you see it | Mostly the United States | International; commonly Canada | Some orthodontic and surgical records |
If a dentist, insurer, referral, or treatment plan gives you a tooth number, use the converter above to confirm the tooth's location. For treatment decisions, rely on the notation in your own dental record and ask the treating dental professional if anything is unclear.
Search dental offices by city, see phone numbers, opening hours and specialists, and call in one tap.
The Universal system numbers permanent teeth 1–32 and primary teeth A–T, and is most common in the United States. FDI/ISO uses two digits, where the first digit is the quadrant and the second is the tooth's position from the centre of the mouth. FDI/ISO is the international standard (ISO 3950) and is commonly seen in Canada.
Usually, people using that phrase mean FDI/ISO two-digit notation. The formal ISO standard is a two-digit designation system, not a separate standard named “Canadian.”
Universal #19 is the lower-left first molar. Its FDI/ISO number is 36 and its Palmer notation is LL6.
The first digit, 3, is the permanent lower-left quadrant. The second digit, 6, is the first molar. FDI 36 is Universal #19.
In the Universal system the wisdom teeth are #1, #16, #17 and #32. In FDI/ISO they are 18, 28, 38 and 48.
There are 20 primary teeth. Universal notation labels them A through T. FDI/ISO uses quadrants 5 to 8 and positions 1 to 5, so the primary central incisors are 51, 61, 71 and 81.
No. A missing tooth keeps its number, so the rest of your chart stays consistent. If you are unsure which system your dentist is using, ask them to confirm it.
Dental Digital Marketing Agency
Copyright © 2026 The Smile Insider. All Rights Reserved.
In partnership with Reveation Labs – Innovating around “Dentist Near Me”.
