The FDI tooth numbering system names every tooth with two digits: the first digit is the quadrant and the second is the tooth, counted from the midline. Quadrants 1 to 4 are the permanent teeth (upper right, upper left, lower left, lower right) and 5 to 8 are the same quadrants for primary teeth. So 36 is the lower left first molar, 48 the lower right wisdom tooth and 85 the lower right primary second molar.
How does FDI tooth numbering work?
The two-digit system was adopted by the FDI World Dental Federation and is published as the international standard ISO 3950. It is widely used in India, on charts, case papers, lab slips and X-ray labels. Every tooth gets exactly one number, made of two parts:
- First digit: the quadrant. The mouth is split into four quadrants. Number them clockwise as you face the patient, starting with the patient’s upper right.
- Second digit: the position. Count from the midline backwards: 1 is the central incisor and 8 is the third molar (1 to 5 in primary teeth).
| First digit (permanent) | First digit (primary) | Quadrant |
|---|---|---|
| 1 | 5 | Upper right |
| 2 | 6 | Upper left |
| 3 | 7 | Lower left |
| 4 | 8 | Lower right |
| Second digit | Permanent tooth | Primary tooth |
|---|---|---|
| 1 | Central incisor | Central incisor |
| 2 | Lateral incisor | Lateral incisor |
| 3 | Canine | Canine |
| 4 | First premolar | First molar |
| 5 | Second premolar | Second molar |
| 6 | First molar | — |
| 7 | Second molar | — |
| 8 | Third molar (wisdom tooth) | — |
Note the trap in the primary column: in a child, position 4 is a molar, not a premolar, because primary teeth have no premolars.
Five examples, read step by step
| FDI | How to read it | Tooth | Universal | Palmer |
|---|---|---|---|---|
| 11 | Quadrant 1 (upper right), position 1 | Upper right central incisor | 8 | UR 1 |
| 36 | Quadrant 3 (lower left), position 6 | Lower left first molar | 19 | LL 6 |
| 48 | Quadrant 4 (lower right), position 8 | Lower right third molar (wisdom tooth) | 32 | LR 8 |
| 55 | Quadrant 5 (upper right, primary), position 5 | Upper right primary second molar | A | UR E |
| 85 | Quadrant 8 (lower right, primary), position 5 | Lower right primary second molar | T | LR E |
Read each number as two digits — “three-six”, not “thirty-six” — so it is never confused with a Universal number. You can check any tooth instantly with the free tooth numbering converter, which shows FDI, Universal and Palmer side by side on a clickable chart.
How do FDI, Universal and Palmer compare?
| FDI (ISO 3950) | Universal | Palmer | |
|---|---|---|---|
| Format | Two digits: quadrant + position | One number per tooth | Quadrant bracket + position |
| Permanent teeth | 11–18, 21–28, 31–38, 41–48 | 1–32 | 1–8 in each quadrant |
| Primary teeth | 51–55, 61–65, 71–75, 81–85 | Letters A–T | Letters A–E in each quadrant |
| Where you meet it | India and most of the world | Mainly the United States | UK and orthodontic texts |
| Lower left first molar | 36 | 19 | LL 6 |
Universal numbers permanent teeth in one run: 1 is the upper right third molar, it crosses the upper arch to 16 (upper left third molar), drops to 17 (lower left third molar) and ends at 32 (lower right third molar). Primary teeth run A to T in the same order. Palmer draws the quadrant as a small bracket around the number; in typed notes it is usually written UR, UL, LL or LR, as in “LL 6”.
FDI to Universal: a table you can work out yourself
For permanent teeth, take the second FDI digit n: quadrant 1 is 9 − n, quadrant 2 is 8 + n, quadrant 3 is 25 − n and quadrant 4 is 24 + n. For example, 36 is 25 − 6 = 19, and 48 is 24 + 8 = 32.
| Position | Upper right | Upper left | Lower left | Lower right |
|---|---|---|---|---|
| 1 Central incisor | 11 → 8 | 21 → 9 | 31 → 24 | 41 → 25 |
| 2 Lateral incisor | 12 → 7 | 22 → 10 | 32 → 23 | 42 → 26 |
| 3 Canine | 13 → 6 | 23 → 11 | 33 → 22 | 43 → 27 |
| 4 First premolar | 14 → 5 | 24 → 12 | 34 → 21 | 44 → 28 |
| 5 Second premolar | 15 → 4 | 25 → 13 | 35 → 20 | 45 → 29 |
| 6 First molar | 16 → 3 | 26 → 14 | 36 → 19 | 46 → 30 |
| 7 Second molar | 17 → 2 | 27 → 15 | 37 → 18 | 47 → 31 |
| 8 Third molar | 18 → 1 | 28 → 16 | 38 → 17 | 48 → 32 |
Primary teeth convert to letters: 51–55 are E to A, 61–65 are F to J, 71–75 are O to K and 81–85 are P to T. So 55 is A, 65 is J, 75 is K and 85 is T. Palmer is the easiest of all: keep the position digit (or the letter A–E for primary teeth, counting from the central incisor) and write the quadrant in front of it.
What are the most common tooth-numbering mistakes?
- Reading 11 as “eleven”. In the Universal system 11 is the upper left canine (FDI 23). Always say the digits separately.
- Swapping left and right. A chart is drawn as if you are facing the patient, so the patient’s right side is on your left. Quadrant 1 sits at the top left of the page.
- Using a permanent number for a milk tooth. In a child, a primary second molar is 75, not 35. Write the 5–8 quadrant digits for every primary tooth, and note it when a primary and a permanent tooth are both present in the same area.
- Counting teeth to find the number. The number names the tooth, not its place in the row. If 36 is missing, the next molar is still 37.
- Mixing systems in one record. A referral from abroad that says “#19” means FDI 36. Convert it once, and write the system next to the number when you copy it.
- Palmer without the quadrant. A bare “6” could be any of four first molars. Always write UR, UL, LL or LR.
- Inventing numbers for extra teeth. Describe a supernumerary tooth in words next to the nearest tooth number instead of giving it a number of your own.
Where does the tooth number need to be right?
A wrong number in one place travels everywhere else. Check the tooth number, and read it back, wherever it leaves the chart:
- Treatment plans and estimates — each line should name the tooth, so the patient and the front desk know what was agreed.
- Consent forms — an extraction or a root canal consent should state the tooth number. See what a dental consent form should include.
- Lab slips — the crown, the bridge abutments and the shade all hang on the tooth number.
- X-ray labels and referral letters — another dentist will read them without you in the room.
- Old paper records — when you move case papers into software, convert any Universal or Palmer notes to FDI once. Our guide to moving from paper records to dental software covers the rest of that job.
How do you say tooth numbers when dictating?
Say the tooth first, then the finding: “three-six deep distal caries”, “two-four irreversible pulpitis”. Pause between teeth so each finding stays separate. Many Indian dentists mix English terms with Hindi or Gujarati — “36 number me caries hai” — and good voice charting should cope with that. You can try it in the free voice dental chart, which accepts FDI numbers, spoken numbers, Palmer (such as LL6) and tooth names. Our guide to voice charting in dentistry explains the workflow.
How Odontra uses FDI numbering
Odontra’s treatment planner is built on an FDI tooth chart, every procedure is tied to a tooth and a status, and lab work is linked to the patient and the tooth. With voice charting, you can dictate findings in English, Hindi, Gujarati or a mix, and each one lands on the right tooth after you approve it. Keep the tooth numbering converter open for referrals that use another system, or book a demo to see the chart with your own cases.