Tread Depth Difference Calculator
Compare measured remaining tread between two tires. Get the gap in 32nds and mm, plus the diameter and circumference gap it creates.
Compare measured remaining tread.
Tread Depth Difference Calculator: Tire Size Inputs
Compare two tire sizes here. Use the formulas and reference tables below for this tool's specific calculation.
How Tread Depth Difference Calculator Works?
The Tread Depth Difference Calculator works by subtracting one tread reading from the other and converting the gap into diameter and circumference. The tool uses 3 steps.
Enter both readings
Type the tread depth of each tire, for example 9/32 in and 6/32 in.
Find the gap
The calculator returns a 3/32 in (2.4 mm) gap.
Convert to size
The calculator doubles the gap for diameter (4.8 mm) and multiplies by π for circumference (15.0 mm, 0.59 in).
Tread Depth Difference Calculator Formula
The Tread Depth Difference Calculator formula is ΔTD = TD₁ − TD₂, and the size effects are ΔOD = 2 × ΔTD and ΔC = 2π × ΔTD.
ΔTD = TD₁ − TD₂ΔOD = 2 × ΔTDΔC = 2π × ΔTD- TD₁, TD₂
- Tread depth readings (mm)
- ΔOD
- Diameter gap (mm)
- ΔC
- Circumference gap (mm)
Worked example
Readings of 11/32 in and 5/32 in give a gap of 6/32 in (4.8 mm). The diameter gap is 9.5 mm (0.38 in), and the circumference gap is 29.9 mm (1.18 in).
Tread Depth Difference Calculator Conversion Table
The Tread Depth Difference Calculator conversion table converts 7 pairs of tread readings into tread, diameter and circumference gaps.
| Readings | Tread gap (in) | Tread gap (mm) | Diameter gap | Circumference gap |
|---|---|---|---|---|
| 10/32 vs 9/32 | 1/32 in | 0.8 mm | 1.6 mm | 5.0 mm |
| 10/32 vs 8/32 | 2/32 in | 1.6 mm | 3.2 mm | 10.0 mm |
| 10/32 vs 7/32 | 3/32 in | 2.4 mm | 4.8 mm | 15.0 mm |
| 9/32 vs 6/32 | 3/32 in | 2.4 mm | 4.8 mm | 15.0 mm |
| 8/32 vs 4/32 | 4/32 in | 3.2 mm | 6.3 mm | 19.9 mm |
| 11/32 vs 5/32 | 6/32 in | 4.8 mm | 9.5 mm | 29.9 mm |
| 6/32 vs 6/32 | 0/32 in | 0.0 mm | 0.0 mm | 0.0 mm |
What is Tread Depth Difference Calculator?
A Tread Depth Difference Calculator is a tool that measures the gap in remaining tread between 2 tires and shows the size difference the gap creates. Tread wear shrinks a tire's diameter by twice the tread lost.
Gaps matter most on the same axle and on AWD vehicles. A 2/32 in gap between left and right tires makes the open differential work on every mile.
The calculator uses readings from the same groove position on each tire for a fair comparison.
What are the uses of Tread Depth Difference Calculator?
There are 4 main uses of the Tread Depth Difference Calculator, including axle pairing and AWD checks.
Axle pairing
Pair the closest-matched tires on one axle.
AWD checks
Compare the gap with the AWD maker's limit.
Rotation decisions
Find the tires to move to the drive axle.
Shop disputes
Document tread gaps on replaced tires.
Related Tread Wear & Tire Life Tools
View All 134 Subtools →Convert millimeters and thirty-seconds of an inch.
Estimate diameter reduction from tread loss.
Compare tread with a selected replacement threshold.
Calculate measured wear per distance.
Compare tread readings across wheel positions.
Calculate age from a DOT date code.