Plus-Two Tire Size Calculator

This calculator works by adding 2 in to the rim diameter and finding the size that holds the original overall diameter. It removes about 25.4 mm (1 in) from each sidewall.

1. Enter the original size, for example 225/60R17 (27.63 in).
2. Let the tool test 19 in sizes.
3. Read the best Plus-2 match: 245/45R19 at 27.68 in.
4. Check the change: +0.19%.

The formula keeps D_new ≈ D_old with Rim_new = Rim_old + 2.

Worked example for 205/60R16: sidewall is 123 mm. After a 25.4 mm cut it is 97.6 mm. On a 215 mm width, the aspect ratio is 45.4%, so 215/45R18 (25.62 in) is the match.

The conversion table gives the closest Plus-2 size for 10 original sizes. The largest gap is −0.52% (235/55R18 to 255/40R20).

Plus-2 matches often need a 10–30 mm wider tire. The original 245/40R18 is the exception: 245/30R20 keeps the width.

The Plus-Two Tire Size Calculator is a tool that finds tire sizes for a wheel 2 in larger than stock at the same overall diameter. Plus-2 is a styling and performance upgrade with a clear ride-quality cost.

Each sidewall loses about 1 in (25.4 mm). On a car with a 4.5 in sidewall, that leaves about 4.0 in after Plus-1 and 3.5 in after Plus-2.

This calculator has 4 uses: styling upgrades, big-brake kits, performance setups and wheel resale checks.

• Upgrade styling: Fit larger wheels with the same speedometer accuracy.
• Clear big-brake kits: Make room for 355 mm (14 in) or larger rotors.
• Build performance setups: Lower sidewall flex for track days.
• Check resale wheels: Confirm tire sizes for used 2 in larger wheels.