How Old Are My Tires? Reading the DOT Date Code
Where the DOT code is, and why you may not find it
Every tire carries a Tire Identification Number — the string that starts with the letters DOT. Federal rule 49 CFR 574.5 requires the manufacturer to mold it "on one sidewall of each tire", and a new tire's TIN is thirteen symbols. Note the wording: one sidewall. The full number is only required on a single side, so if you crouch down and cannot see it, the tire is very likely mounted with that side facing inward — check the same tire from under the car, or look at the opposite wheel. The last four digits are the ones that tell you the age.
What the regulation actually says
Tire age gets explained a lot, and three details go wrong almost every time. All three are settled in one paragraph of 49 CFR 574.5.
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Commonly claimedThe four digits are the week and year, so 0109 is roughly early January 2009.
VerifiedIt is more exact than "roughly", and the regulation works this very example. It requires the first two symbols to identify "the week of the year by using 01 for the first full calendar week in each year, 02 for the second full calendar week, and so on", with the calendar week running "from Sunday through the following Saturday". Its own worked example: "0109 means the tire was manufactured in the first full calendar week of 2009, or the week beginning on Sunday, January 4, 2009." Note the word FULL — a partial week at the start of January is not week 01, which is why the date lands later than people expect.
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Commonly claimedA DOT number is a fixed length, so you can count characters to find the date.
VerifiedCount from the END instead. §574.5 sets the new-tire TIN at thirteen symbols, but a RETREADED tire's TIN is only seven, and the rule notes that specific Federal Motor Vehicle Safety Standards "may have more specific TIN marking requirements for some tires". What is constant is the position: the date code "is the final group". The last four digits are the date on any of them.
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Commonly claimedTires legally expire after six years.
VerifiedNo federal standard sets an expiry date. 49 CFR 574.5 defines how the date must be MARKED and says nothing about how long a tire may be used. The six-year and ten-year figures that circulate are guidance from vehicle and tire manufacturers, and they disagree with each other — which is why your owner's manual is the right place to look rather than a blog. Treat the date code as one input alongside tread depth and visible cracking, not as a use-by date printed by law.
Reading the date, step by step
Find the DOT string on the sidewall. Ignore everything except the final four digits. The first two are the week — 01 through 52, occasionally 53, because the regulation allows the final week of each year to "include no more than six days of the following year". The last two are the last two digits of the year. So 3621 is the 36th full week of 2021, which is early September. 0518 is the fifth full week of 2018, early February. If you find only three digits at the end, the tire was made before 2000 and should be replaced regardless of how it looks — that format was discontinued a quarter of a century ago.
What to do with the number once you have it
Age matters most for tires that have not worn out: a spare that has never touched the road, a second set of winter tires, a low-mileage car, a trailer that sits for months. Rubber degrades with time and heat whether or not it is being used, so a tire with deep tread and a date code from a decade ago is a different proposition from a tire with deep tread from last year. Check the date against your owner's manual guidance, then look at the tire itself — sidewall cracking, tread depth, and any bulging or uneven wear. The date is a prompt to inspect, not a verdict on its own.
Related references on this site
Once you have the age, the sidewall's other markings tell you the rest: our tire size decoder breaks down what 225/55R17 98H actually specifies, including the load index and speed rating. The tire pressure reference lists recommended cold pressures by vehicle, and the TPMS reset procedures cover relearning sensors after a rotation or a new set.
Frequently Asked Questions
Where exactly is the DOT code on a tire?
On the sidewall, starting with the letters DOT. 49 CFR 574.5 requires the full Tire Identification Number on one sidewall only, so if you cannot see it on the side facing you, it is on the inboard face — look at the same tire from under the vehicle.
What do the last four digits of the DOT number mean?
Week and year of manufacture. The first two identify the week, counting 01 as the first FULL calendar week of that year and running Sunday to Saturday; the last two are the final two digits of the year. The regulation gives 0109 as meaning the week beginning Sunday, January 4, 2009.
Do tires expire?
Not by federal rule. 49 CFR 574.5 governs how the date is marked, not how long a tire may be used. Replacement-age guidance comes from vehicle and tire manufacturers and varies between them, so check your owner's manual and judge the tire on tread depth and condition as well as age.
My tire only has three digits at the end. Why?
It was manufactured before 2000, when the year was encoded with a single digit. Tires that old should be replaced regardless of appearance or remaining tread.
Sources
Documents this guide was checked against. How we verify.