Tire Tread Depth Converter
Convert tire tread depth between 32nds of an inch, decimal inches and millimeters. Includes legal minimum and replacement thresholds.
Convert millimeters and thirty-seconds of an inch.
Tire Tread Depth Converter: Tire Size Inputs
Compare two tire sizes here. Use the formulas and reference tables below for this tool's specific calculation.
How Tire Tread Depth Converter Works?
The Tire Tread Depth Converter works by dividing 32nds by 32 to get inches and multiplying inches by 25.4 to get millimeters. The tool uses 3 steps.
Pick the input unit
Choose 32nds of an inch or millimeters.
Enter the reading
Type the gauge reading, for example 5/32 in.
Read all units
The converter returns 0.156 in and 4.0 mm, with the nearest threshold label.
Tire Tread Depth Converter Formula
The Tire Tread Depth Converter formula is mm = (n ÷ 32) × 25.4 = n × 0.79375.
mm = n × 0.79375n = mm ÷ 0.79375in = n ÷ 32- n
- Tread depth in 32nds of an inch
- 0.79375
- Millimeters per 1/32 in
Worked example
A reading of 7/32 in equals 5.6 mm (0.219 in). A European reading of 3 mm equals 3.8/32 in, just under 4/32 in.
Tire Tread Depth Converter Conversion Table
The Tire Tread Depth Converter conversion table converts 14 tread depths from 2/32 in to 18/32 in and marks common reference points.
| 32nds | Decimal inch | Millimeters | Reference point |
|---|---|---|---|
| 2/32 in | 0.0625 in | 1.6 mm | Legal minimum (US, EU 1.6 mm) |
| 3/32 in | 0.0938 in | 2.4 mm | — |
| 4/32 in | 0.1250 in | 3.2 mm | Wet-road replacement advice |
| 5/32 in | 0.1562 in | 4.0 mm | — |
| 6/32 in | 0.1875 in | 4.8 mm | Snow replacement advice |
| 7/32 in | 0.2188 in | 5.6 mm | — |
| 8/32 in | 0.2500 in | 6.3 mm | — |
| 9/32 in | 0.2812 in | 7.1 mm | — |
| 10/32 in | 0.3125 in | 7.9 mm | New (passenger) |
| 11/32 in | 0.3438 in | 8.7 mm | — |
| 12/32 in | 0.3750 in | 9.5 mm | — |
| 14/32 in | 0.4375 in | 11.1 mm | — |
| 16/32 in | 0.5000 in | 12.7 mm | New (light truck) |
| 18/32 in | 0.5625 in | 14.3 mm | — |
What is Tire Tread Depth Converter?
A Tire Tread Depth Converter is a tool that converts tread depth between the US unit of 32nds of an inch and the metric unit of millimeters. US gauges read in 32nds, and European and Asian gauges read in millimeters.
The legal minimum in the United States (most states) and the European Union is 2/32 in or 1.6 mm. Tire makers and safety groups advise replacement at 4/32 in (3.2 mm) for wet roads and 5/32 to 6/32 in (4 to 4.8 mm) for snow.
Tread wear indicator bars molded into the grooves sit at 2/32 in (1.6 mm).
What are the uses of Tire Tread Depth Converter?
There are 4 main uses of the Tire Tread Depth Converter, including gauge reading and inspection rules.
Gauge reading
Read a metric gauge in 32nds or the reverse.
Inspection rules
Compare a reading with a legal limit in another unit.
Spec sheets
Convert new tread depth from a data sheet.
Used tire listings
Compare listings that use different units.
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