Custom Plus-Sizing Calculator
Explore any plus or minus wheel size change from −2 to +4 inches. Get the closest tire size, sidewall height and diameter gap for each step.
Explore specified wheel diameter increases.
Custom Plus-Sizing Calculator: Tire Size Inputs
Compare two tire sizes here. Use the formulas and reference tables below for this tool's specific calculation.
How Custom Plus-Sizing Calculator Works?
The Custom Plus-Sizing Calculator works by applying any wheel size change you choose, from −2 to +4 inches, and solving for the closest-diameter tire at each step. The tool uses 4 steps.
Enter the stock size
Type the original size, for example 215/60 R16.
Choose the step
Enter a wheel change such as +3, or a range such as −2 to +4.
Set allowed widths
Choose the widths the vehicle accepts, for example 215 to 245 mm.
Compare every step
The calculator lists the best size, the sidewall and the diameter gap for each step.
Custom Plus-Sizing Calculator Formula
The Custom Plus-Sizing Calculator formula is SH_n = SH₀ − n × 12.7 mm for a wheel change of n inches.
Rim_n = Rim₀ + nSH_n = SH₀ − 12.7 × nAR_n = SH_n ÷ W × 100- n
- Wheel diameter change in inches (negative for minus sizing)
- SH₀
- Stock sidewall (mm)
- W
- Chosen width (mm)
Worked example
A 215/60 R16 tire has a 129 mm sidewall. A +3 change to a 19-inch wheel needs 129 − 38.1 = 90.9 mm. On a 225 mm width, 90.9 ÷ 225 = 40.4%, so the closest size is 225/40 R19 at 662.6 mm (−0.27%).
Custom Plus-Sizing Calculator Conversion Table
The Custom Plus-Sizing Calculator conversion table shows the best tire size for 7 wheel steps from 14 to 20 inches, using 215/60 R16 as stock.
| Wheel change | Best size | Sidewall | Diameter | Gap |
|---|---|---|---|---|
| -2 (14 in) | 235/65 R14 | 152.8 mm | 661.1 mm | -0.50% |
| -1 (15 in) | 235/60 R15 | 141.0 mm | 663.0 mm | -0.21% |
| +0 (16 in) | 215/60 R16 | 129.0 mm | 664.4 mm | +0.00% |
| +1 (17 in) | 235/50 R17 | 117.5 mm | 666.8 mm | +0.36% |
| +2 (18 in) | 235/45 R18 | 105.8 mm | 668.7 mm | +0.65% |
| +3 (19 in) | 225/40 R19 | 90.0 mm | 662.6 mm | -0.27% |
| +4 (20 in) | 225/35 R20 | 78.8 mm | 665.5 mm | +0.17% |
What is Custom Plus-Sizing Calculator?
A Custom Plus-Sizing Calculator is a tool that finds matching tire sizes for any wheel diameter change, not only +1 and +2. Owners of SUVs and trucks often jump 3 or 4 inches in wheel size, and some owners step down for winter.
Each 1-inch step removes 12.7 mm (0.5 in) of sidewall. A +4 change removes 50.8 mm (2.0 in), which pushes many vehicles below a 90 mm sidewall.
The calculator shows every step in one table, so the owner sees where sidewall height becomes too thin for the roads driven.
What are the uses of Custom Plus-Sizing Calculator?
There are 4 main uses of the Custom Plus-Sizing Calculator, including large SUV wheel upgrades and multi-step planning.
Large SUV wheel upgrades
Size tires for +3 and +4 wheels on SUVs and pickups.
Multi-step planning
Compare several wheel sizes before choosing one.
Minus sizing
Enter negative steps for winter or off-road wheels.
Sidewall limits
Find the largest wheel that keeps a chosen minimum sidewall.
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