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How to Measure Tire Tread Depth
A practical guide for collecting safer, more consistent tread depth measurements.
Key Facts About Tread Depth Measurement
- Tread depth should be measured consistently across the tire and recorded in the same unit system.
- Multiple readings are usually more useful than one isolated reading because tire wear is often uneven.
- Measurement consistency affects wear-rate estimates, remaining tread projections, and report quality.
- Tread depth alone does not determine whether a tire is legal, safe, roadworthy, or serviceable.
- Visible damage, cracking, bulges, exposed cords, punctures, or abnormal wear should be inspected by a qualified tire professional.
Definition
Tread depth: The measured depth of remaining tire tread, commonly expressed in 32nds of an inch or millimeters. It is one useful tire condition measurement, but it must be interpreted with tire age, damage, inflation, alignment, load, and operating conditions.
Use the right tool
Use a tire tread depth gauge. Do not rely on photos, coins, phone apps, or visual guessing when you need a value for wear-rate calculations.
Record measurements in either 32nds of an inch or millimeters. Keep the same unit for the entire tire.
Measure by groove and position
Most tires have fewer than 8 measurable main grooves. Measure only the grooves that actually exist on the tire.
For a quick check, one position around the tire can be used. For a better average, measure up to three positions around the tire, approximately 120 degrees apart, when that can be done safely.
Example: a tire with 4 measurable grooves and 3 positions produces 12 measurements. A tire with 8 grooves and 3 positions produces the maximum 24 measurements.
Measuring Tires While They Are Installed on the Vehicle
If you are measuring the tire while it is still installed on the vehicle, park on a level surface, engage the parking brake, and place wheel chocks on the wheels remaining on the ground before taking any measurements.
In many cases, you can safely measure at least two tread depth locations without raising the vehicle. If additional measurement points cannot be reached safely, do not attempt to force access.
If you choose to raise the vehicle, use only the manufacturer-recommended lifting points and always support the vehicle with properly rated jack stands. Never rely on a hydraulic jack alone and never place any part of your body under an unsupported vehicle.
If you cannot safely reach all measurement locations, record the measurements you can safely obtain or have the tire inspected by a qualified tire professional.
How to use the average
The measurement average is a better input than a single tread reading because it reduces the effect of one unusual groove or one unusual point around the tire.
Use the calculated average as the current average tread depth in Treadsley wear-rate tools.
Related Knowledge and Tools
Related Tool
Average multiple tread depth readings before using them in wear-rate or report calculations.
Open averaging toolRelated Report Tool
Create a personal, non-commercial multi-tire wear report from tread depth and mileage data.
Open multi-tire reportImportant safety and limitation notice
This guide is for general educational use. It does not determine whether a tire is legal, safe, roadworthy, repairable, or acceptable for continued use.
Tire serviceability can be affected by tread depth, age, cracking, punctures, exposed cords, sidewall damage, bulges, impact damage, inflation pressure, load, alignment, and operating conditions. Have questionable tires inspected by a qualified tire professional.