Target Diameter Tire Calculator
Solve for the aspect ratio that gives a target tire diameter on your chosen width and rim. Get the exact and nearest standard size.
Solve for nominal aspect ratio.
Target Diameter Tire Calculator: Tire Size Inputs
Compare two tire sizes here. Use the formulas and reference tables below for this tool's specific calculation.
How Target Diameter Tire Calculator Works?
The Target Diameter Tire Calculator works by rearranging the diameter formula to solve for aspect ratio, given a target height, a width and a rim size. The tool uses 4 steps.
Enter the target diameter
Type the desired height in inches or millimeters, for example 33 in (838.2 mm).
Enter width and rim
Type the section width (285 mm) and rim diameter (17 in).
Solve for aspect ratio
The calculator returns an exact aspect ratio of 71.3%.
Round to a real size
The calculator rounds to 285/70 R17 and shows that size's diameter of 32.71 in.
Target Diameter Tire Calculator Formula
The Target Diameter Tire Calculator formula is AR = (OD_target − Rim × 25.4) ÷ (2 × W) × 100.
SH = (OD_target − Rim × 25.4) ÷ 2AR = SH ÷ W × 100AR_std = round(AR ÷ 5) × 5- OD_target
- Desired overall diameter (mm)
- W
- Chosen section width (mm)
- Rim
- Chosen rim diameter (in)
Worked example
A 31-inch (787.4 mm) target on a 265 mm width and 17-inch rim needs a sidewall of (787.4 − 431.8) ÷ 2 = 177.8 mm. The aspect ratio is 177.8 ÷ 265 × 100 = 67.1%, so the nearest real size is 265/65 R17 at 30.56 in or 265/70 R17 at 31.61 in.
Target Diameter Tire Calculator Conversion Table
The Target Diameter Tire Calculator conversion table solves the required aspect ratio for 9 target diameters and rounds each result to a standard size.
| Target diameter | Width | Rim | Exact aspect ratio | Nearest standard size |
|---|---|---|---|---|
| 26 in (660 mm) | 225 mm | 18 in | 45.2% | 225/45 R18 = 25.97 in |
| 26 in (660 mm) | 245 mm | 18 in | 41.5% | 245/40 R18 = 25.72 in |
| 28 in (711 mm) | 225 mm | 17 in | 62.1% | 225/60 R17 = 27.63 in |
| 29 in (737 mm) | 245 mm | 17 in | 62.2% | 245/60 R17 = 28.57 in |
| 31 in (787 mm) | 265 mm | 17 in | 67.1% | 265/65 R17 = 30.56 in |
| 32 in (813 mm) | 275 mm | 18 in | 64.7% | 275/65 R18 = 32.07 in |
| 33 in (838 mm) | 285 mm | 17 in | 71.3% | 285/70 R17 = 32.71 in |
| 33 in (838 mm) | 305 mm | 18 in | 62.5% | 305/60 R18 = 32.41 in |
| 35 in (889 mm) | 315 mm | 17 in | 72.6% | 315/75 R17 = 35.60 in |
What is Target Diameter Tire Calculator?
A Target Diameter Tire Calculator is a tool that finds the aspect ratio needed to reach a chosen tire height on a chosen width and rim. Most calculators go from size to diameter. The Target Diameter Tire Calculator goes from diameter to size.
Aspect ratios come in steps of 5, so the exact answer almost always lands between 2 real sizes. The calculator shows both neighbors and their diameter gaps.
Truck owners use the tool to hit an inch-height goal, and car owners use the tool to hold the stock height on a new wheel.
What are the uses of Target Diameter Tire Calculator?
There are 4 main uses of the Target Diameter Tire Calculator, including lift kit tire selection and wheel swaps.
Lift kit tire selection
Find a metric size that reaches a 33-inch or 35-inch goal.
Wheel swaps
Find the series that keeps stock height on a new rim size.
Wider tires
Find the series that offsets the added height of a wider tire.
Gear ratio planning
Lock in a target height before choosing an axle ratio.
Related Wheel Sizing & Conversion Tools
View All 134 Subtools →Find sizes near a target diameter.
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Explore specified wheel diameter increases.