Tyre DOT Code Explained — How to Read the Date Code (2026)

Tyre (tire) DOT code: the quick answer

The tyre DOT code, or Tyre Identification Number (TIN), ends in a four-digit date code. The first two digits give the week and the last two give the year. For example, the code ending in the digits for week one of year nine means the first full week of 2009. The full code is moulded on only one sidewall, so on a fitted wheel you may have to look at the side facing under the car.

Where the DOT code is on the sidewall

US federal rules (49 CFR 574.5) require the maker of a new tyre to mould a 13-symbol TIN permanently into one sidewall. Nothing requires it on the other side. If the outer face of your tyre shows “DOT” and a short code, or no code at all, the full number is on the inner face. Use a torch, or turn the steering to full lock to reach the front tyres.

The regulation also says where the TIN goes and how large it must be:

• Position: the lower part of the sidewall, between the widest point of the tyre and the bead (the edge that sits on the rim), placed so the rim flange does not cover it.
• Size and depth: 49 CFR 574.5 sets minimum character heights and moulding depths. Smaller tyres, by section width or bead diameter, may use smaller characters.
• Spacing: where the DOT mark is used, it sits a short set distance from the TIN, either to its left or above or below it, as set out in 49 CFR 574.5.
• Laser-etched dates: instead of moulding the date code, the maker may laser-etch it, within the depth and time limits in 49 CFR 574.5. As a result, the date can look shallower or slightly different from the characters next to it.

How to read the four-digit date code

The date code is always the last group of the TIN and always uses four numbers:

• Digits 1–2: the week. The first pair is the first full calendar week of the year, the next pair the second, and so on. Each week runs from Sunday to Saturday.
• Digits 3–4: the year, as its last two digits.

The regulation’s own example is the week from Sunday 4 January to Saturday 10 January 2009. Week one starts on the first Sunday of the year, so a tyre made in the first days of January can carry the previous year’s final week. The rules allow the last week of a year to include up to six days of the next year.

To work out the age, take the current year (2026) and subtract the year in the code, then adjust for the week. Check every tyre, including the spare. Tyres bought as a set can come from different production weeks.

What the rest of the TIN means

The date code is the only part that tells you the age. The other groups are for traceability, for example in a recall:

• Plant code (3 symbols): NHTSA assigns this code to identify the manufacturer or retreader.
• Manufacturer’s code (6 symbols): it can describe the tyre’s size, characteristics or brand owner, but only the manufacturer keeps the key, which it must give to NHTSA on request. Do not try to read the tyre size from it. The size is printed separately, as explained in the tyre size guide.
• Letters used: a TIN may only contain A, B, C, D, E, F, H, J, K, L, M, N, P, R, T, U, V, W, X, Y and the digits 0–9. Letters like O and I are left out, so a round character is a zero.

Older codes look different. Makers that had a two-symbol plant code could keep using it until 13 April 2025. Those tyres show a two-symbol plant code, a short size code, an optional short code, and then the four-digit date. The total length varies, but the date is still the last four digits.

Retreads carry a seven-symbol TIN: a three-symbol plant code followed by the four-digit date code, with an “R” marked next to it. On a retread, the date shows when the tyre was retreaded, not when the original casing was made.

DOT codes on tyres in the UK, Canada and Australia

The DOT symbol certifies that a tyre meets a US Federal Motor Vehicle Safety Standard, and the TIN layout above is a US rule. Many tyres sold in the UK, Canada and Australia carry the DOT symbol and TIN as well as their local approval marks. On those tyres, the reading method above works exactly the same. If a tyre has no DOT symbol, look in the same lower-sidewall area for a separate four-digit group, often in a small oval, and read it the same way: week, then year. If you can’t find a date code at all, ask the fitter to show it to you before you accept the tyre.

Drive, check or replace?

When you buy replacements, confirm the size on the sidewall and in the handbook. The tyre size calculator shows whether an alternative size changes the rolling diameter.

Sources

• 49 CFR 574.5, Tire identification requirements (NHTSA, US Department of Transportation), via eCFR and the official published edition on govinfo.gov.