How to use this calculator
Record an earlier depth, a later depth and the distance driven between them. Keep a log of the tire identity, groove or measurement location, date and odometer reading so you can repeat the comparison. Subtract the earlier odometer reading from the later reading before entering distance. Use a tread depth gauge, and inspect multiple points separately rather than treating one reading as the condition of the whole tire. Repeat this calculation for each matched location or measurement interval you want to compare.
This is a retrospective measurement summary, not remaining tire life, a replacement date or a safe-driving distance. A constant future wear rate is not established by two readings. Tire damage, age, uneven wear and operating conditions are not evaluated. Follow applicable tire and vehicle guidance and have concerning wear or damage inspected; a small calculated rate does not establish that a tire is safe. Zero loss means no difference in the entered readings, not unlimited service life.
The formula
A worked example
Suppose a matching location measures 8.0 mm, then 7.0 mm after 5,000 miles. Observed loss is 1.0 mm. The rate is 1 ÷ 5,000 × 1,000 = 0.20 mm per 1,000 miles, or about 0.1243 mm per 1,000 km. As a separate inch example, 10/32 falling to 8/32 over 10,000 miles loses 2/32 = 1.5875 mm: 0.15875 mm per 1,000 miles. These are hypothetical measured intervals, not tire performance benchmarks.
How the same measured loss changes with distance
Original arithmetic examples for a 1.0 mm loss. These are not expected tire-wear rates or safety thresholds.
| Measured interval (miles) | Loss (mm) | mm per 1,000 miles |
|---|---|---|
| 2,500 | 1.0 | 0.40 |
| 5,000 | 1.0 | 0.20 |
| 10,000 | 1.0 | 0.10 |
Common questions
Does this predict how many miles my tires have left?
No. The tool describes the interval already measured. Extrapolating a two-point average would assume future wear stays the same and would not assess other reasons a tire might need replacement. No remaining-mileage output is provided.
How do I enter tread depth in 32nds?
Select 32nds of an inch and enter the numerator: enter 8 for 8/32 inch, or 7.5 for 7.5/32 inch. Do not enter 0.25 for 8/32 in that mode. Both readings must use the selected unit.
What if the later measurement is larger?
The calculator rejects it as a tread-loss interval. Confirm that the same tire, measurement location and unit were used. Differences in gauge placement, rounding or a changed tire can make readings incomparable; do not turn a negative loss into a positive wear estimate.
Why inspect more than one location?
Depth can vary across a tire. Keep separate matched readings so one location does not hide another. A rate from one pair of readings does not summarize the entire tire or diagnose the cause of uneven wear.
What does zero wear mean?
It means the entered depths are equal. Rounded readings can hide a small change, especially over a short distance. The result does not demonstrate that no rubber was lost, or that future wear will be zero.
How much does measurement rounding matter?
In an original hypothetical example, readings rounded to the nearest 0.1 mm can each differ by up to 0.05 mm from the unrounded value. Their difference can therefore differ by up to 0.1 mm. Over 1,000 miles that alone can change the calculated rate by up to 0.1 mm per 1,000 miles, before other measurement errors.
Can I average several intervals?
For consecutive comparable intervals at the same location, divide total depth loss by total distance and multiply by 1,000. An unweighted average of interval rates is inappropriate when distances differ. Keep the individual readings so changing trends remain visible.
Is this a UTQG treadwear rating calculator?
No. It calculates a rate from your own depth and distance observations. It does not produce a standardized tire grade, mileage warranty result or comparison of tire brands.
Sources & calculation method
Michelin: Tire tread depth explains gauge measurement and checking multiple points across the width. Continental: Tread depth provides additional measurement context. These references support inspection context; neither validates a constant-wear forecast. The loss-over-distance equation above is an arithmetic summary developed for this calculator, not a manufacturer tire-life model.
For a measured distance discrepancy, the Odometer Correction Calculator explains a separate trip-distance adjustment. For nominal size geometry, use Tire Size Comparison. Neither determines tire condition.
References accessed October 5, 2026. No manufacturer endorsement or independent professional review is claimed.
Formula examples and input validation have automated checks. This page has not received an independent automotive professional review. Read our review standards.