How to Read Tire Tread Depth: 32nds of an Inch, Millimeters, and Simple Conversions
How to Read Tire Tread Depth: 32nds of an Inch, Millimeters, and Simple Conversions
Tread depth is commonly expressed in 32nds of an inch in the U.S. That’s why you’ll see numbers like 6/32 or 4/32. In many other places, tread depth is discussed in millimeters (mm).
This guide helps you translate the numbers into decisions you can actually use.
The Units: What Does “6/32” Mean?
“6/32” means six thirty-seconds of an inch. As tread wears down, this number decreases.
Helpful reference points:
Turning a Reading Into an Action
Use a simple rule set:
Full detail: Minimum Tire Tread Depth: Legal vs Safe
The Best Way to Measure (So the Numbers Mean Something)
To avoid misleading readings:
Step-by-step method: How to Measure Tire Tread Depth (Gauge Method)
Why Tread Depth Matters More in the Wet
The tread grooves act like channels to move water away from the contact patch. When the depth is low, the tire may ride on a thin film of water at speed, which reduces real contact with the road. That’s why “legal minimum” can still feel sketchy in heavy rain.
If you want a quick wet-safety screening: