Tire Size Calculator · Practical guide
What Is Plus Sizing for Tires?
Plus sizing pairs a bigger wheel with a lower-profile tire so overall diameter — and your speedometer — stays stock.
At a glance
The Answer
Plus sizing means fitting a larger-diameter wheel with a lower-profile tire while keeping the overall diameter nearly identical to stock. A classic "plus one" upgrade moves from 205/55R16 to 225/45R17: the wheel grows an inch, the sidewall shrinks, and the tire's total height barely changes.
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Tire Size Calculator
Enter your own values, then compare the result with the examples below.
Results
The Math That Keeps It Safe
Stock 205/55R16 measures 24.88 inches tall; the 225/45R17 replacement measures 24.98 inches — a difference of just +0.4%, far inside the 3% tolerance that keeps the speedometer, odometer, and ABS accurate. Verify any plus-size combination in the calculator above before ordering.
Why Drivers Plus Size
- Sharper handling — a shorter sidewall flexes less, improving steering response and cornering stability
- Brake clearance — larger wheels make room for bigger brake kits
- Appearance — more wheel, less rubber fills the fender gap
The trade-offs: a firmer ride, higher tire and wheel cost, and greater vulnerability to pothole damage because there's less sidewall to absorb impacts.
Getting the Aspect Ratio Right
As a rule of thumb, each additional inch of wheel diameter means dropping the aspect ratio by roughly 10-15 points and adding 10-20 mm of width — but rules of thumb are only a starting point. Compute the diameter of the stock size and the candidate size; if the difference is within 3%, the combination is dimensionally sound.
Frequently Asked Questions
What does plus two mean?
Moving up two inches in wheel diameter from stock — for example, 16-inch to 18-inch wheels — with an appropriately lower-profile tire to hold overall diameter steady.
Does plus sizing hurt ride quality?
Yes, somewhat. Less sidewall means less cushioning over bumps, so the ride gets firmer. The effect grows with each plus step.
Will plus sizing void my warranty?
Generally no, as long as the overall diameter stays within the manufacturer's specified range and the tires meet the original load and speed ratings.
Do I need new wheels to plus size?
Yes. Plus sizing by definition uses a larger wheel diameter, so the new tires cannot mount on your existing rims.