When should I replace my tires based on tread depth?

NHTSA says tires are not safe and should be replaced when the tread is worn down to 2/32 of an inch, and Michelin gives 2/32" as the minimum tread depth. Michelin also says wet braking performance begins declining noticeably at 4/32", so replacing at 4/32" gives a safety buffer if you drive often in wet weather.

What does a UTQG Treadwear rating like 200, 400 or 600 mean?

Under NHTSA's 49 CFR 575.104 the treadwear grade is a comparative rating based on the wear rate of the tire on the government test course. A control tire is graded 100, so a tire graded 200 should wear twice as long as the control tire, and one graded 400 four times as long, on that course. It is not a mileage figure.

How is the UTQG treadwear rating tested?

The regulation specifies a government test course (a roughly 400-mile loop near San Angelo, Texas, run for 16 circuits after an 800-mile break-in), and grades are assigned in multiples of 20. Tire manufacturers assign the grades to their own tires under the NHTSA standard.

How do I measure tread depth?

NHTSA suggests the penny test: place a penny in the tread with Lincoln’s head upside down and facing you; if you can see the top of his head, replace your tires. Tires also have built-in treadwear indicators, raised sections between the treads; when the tread is level with them it is time to replace the tires. Michelin notes that a tread depth gauge gives a more precise reading and recommends checking several points across the tire’s width.

What is the difference between treadwear and proration?

Treadwear (UTQG) is a comparative grade of relative wear rate. Proration is a warranty or insurance calculation that turns remaining usable tread into a credit when a tire is replaced early. This calculator focuses on remaining tread depth and the treadwear grade, not warranty terms.

Do all tires have UTQG treadwear ratings?

No. 49 CFR 575.104 applies to new pneumatic tires for passenger cars and does not apply to deep tread tires, winter-type snow tires, space-saver or temporary use spare tires, tires with nominal rim diameters of 12 inches or less, or limited production tires, so a tire without UTQG markings may be in an exempt category.

Tread Depth Calculator & UTQG Treadwear Rating Explainer (2026)

Q: Does treadwear rating predict how many miles I will get?

No. NHTSA says real-world performance may depart significantly from the norm because of driving habits, service practices, road characteristics and climate, and the regulation states no mileage. This page does not give a mileage estimate.

QUICK EXAMPLE

Suppose a tire measured 10/32" when new (an illustrative value; new depth varies by tire) and now measures 6/32". Counting down to the 2/32" replacement depth NHTSA gives, you have used half of the usable tread (4/32" of 8/32"), leaving 50%. Michelin says wet braking performance begins declining noticeably at 4/32", which in this example is 25% usable tread remaining.

Enter the UTQG Treadwear number from your tire sidewall. A control tire is graded 100.

Treadwear Grade (20–1000)Compare with another tire's grade (optional)

Treadwear Grade

400

vs Control Tire (100)

4.0×

calculated: grade ÷ 100

vs Grade 200

2.00×

calculated: 400 ÷ 200

NHTSA: 32% of current tire lines are graded 301 to 400.

NHTSA: treadwear grades are an indication of a tire's relative wear rate; a tire graded 200 should wear twice as long as the control tire on the government test course. It is not a mileage figure, and real-world results can differ because of driving habits, service practices, road characteristics and climate.

Treadwear Grades of Current Tire Lines (NHTSA)

Grade	Share of current tire lines
Below 200	15%
201 to 300	25%
301 to 400	32%
401 to 500	20%
501 to 600	6%
Above 600	2%

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Tire Tread Depth Life Guide

Tread Depth	% Usable Remaining*	Source note
10/32"	100%	Illustrative new depth
8/32"	75%
6/32"	50%
4/32"	25%	Michelin: wet braking performance begins declining noticeably
2/32"	0%	NHTSA: tires are not safe and should be replaced; Michelin: minimum tread depth

*Calculated for an illustrative new depth of 10/32" with 2/32" as the replacement depth. New tread depth varies by tire, so enter your own tire's values in the formula.

How to Use This Calculator

Enter the Original (New) Tread Depth of your tire (new depth varies by tire; check the tire maker’s specification).
Enter the Current / Remaining Tread Depth measured with a tread gauge (or the penny test, which shows when a tire has reached 2/32").
Click 'Calculate Remaining Life'.
Review the remaining usable tread percentage, status band, and replacement recommendation.

Formula & Tread Life Guide

Remaining Usable Tread % = (Current Depth − Replacement Depth) ÷ (Original Depth − Replacement Depth) × 100 Where: • Original Depth is the tread depth when the tire was new • Current Depth is the lowest tread depth measured now • Replacement Depth is 2/32" (about 1.6 mm), the depth at which NHTSA says tires are not safe and should be replaced Example (10/32" new, 4/32" current): Remaining % = (4/32" − 2/32") ÷ (10/32" − 2/32") × 100 = (2 ÷ 8) × 100 = 25% usable tread remaining Depths from official sources: • 2/32" (NHTSA, Michelin): replace the tire; the treadwear indicators are flush with the tread • 4/32" (Michelin): wet braking performance begins declining noticeably; replacing here gives a safety buffer if you drive often in wet weather

About Tread Depth & UTQG Treadwear Ratings

Tread Depth Statements From NHTSA and Michelin

NHTSA says tires are not safe and should be replaced when the tread is worn down to 2/32 of an inch, and to check tread at least once a month when you check pressure. Michelin gives 2/32" (1.6 mm) as the minimum tread depth and says wet braking performance begins declining noticeably at 4/32", when the tire's ability to channel water and resist hydroplaning is already reduced compared with new. Michelin also says tread grooves channel water away from the contact patch.

Understanding UTQG Treadwear Ratings

UTQG (Uniform Tire Quality Grading) treadwear grades are assigned by tire manufacturers under NHTSA's standard, 49 CFR 575.104. The grade is a comparative rating based on the wear rate of the tire on a government test course, with a control tire graded 100: a tire graded 200 should wear twice as long as the control tire on that course. NHTSA says real-world performance may differ from this norm because of driving habits, service practices, road characteristics and climate, so the grade is not a mileage figure. See the UTQG explainer with the full regulation wording for the traction and temperature letters.

Using Tread Depth & UTQG Together

Tread depth tells you how much tread the tire has left today, while the UTQG treadwear grade is a comparison of relative wear rate on the government test course. Use this calculator to track how much usable tread you have left and compare it with the depths NHTSA and Michelin give above. Depth is not the only reason to replace a tire: the age shown by a tire's DOT code is the other number to check.

Frequently Asked Questions

Disclaimer

This tool is for educational and estimation purposes only. Actual safe tread depth can vary with tire type, vehicle, speed, climate, and road conditions. Always follow your tire manufacturer’s guidance, your vehicle’s owner’s manual, and local laws regarding minimum tread depth, and inspect tires regularly for uneven wear or damage.

Tread Depth Calculator & UTQG Treadwear Rating Explainer