How to use the tire size finder
- Enter the tire size your vehicle has now, ideally the one on its door-jamb placard.
- Choose how close the overall diameter should stay, as a percentage either way.
- Tick one or more wheel diameters, and optionally limit the width range.
- Press Find sizes. Results are sorted closest first; open any size in the 3D fitment studio or the tire size calculator.
Worked example
Original 205/55 R16, looking at 17- and 18-inch wheels, widths 205–245 mm, within ±1%:
| Size | Diameter | Difference |
|---|---|---|
| 225/45 R17 | 634.3 mm | +0.38% |
| 215/40 R18 | 629.2 mm | −0.43% |
| 245/35 R18 | 628.7 mm | −0.51% |
| 245/40 R17 | 627.8 mm | −0.65% |
| 205/50 R17 | 636.8 mm | +0.78% |
| 225/40 R18 | 637.2 mm | +0.84% |
The familiar plus-one size 225/45 R17 is on the list. The popular 215/45 R17 isn’t, because it’s 1.04% smaller; widen the tolerance to see it.
What to check next
- Availability: the list is arithmetic; confirm the size is made in the type of tire you want.
- Load index and speed rating must meet the vehicle placard. Read how to read a tire sidewall.
- Rim width: each size has an approved range of wheel widths.
- Clearance: see how the size sits with your wheel’s offset in the 3D fitment studio.
More background in Plus sizing explained.
Frequently asked questions
Where do these sizes come from?
They’re generated from the standard metric pattern: widths ending in 5 from 135 to 355 mm and aspect ratios in steps of 5, on the wheel diameters you choose. It’s arithmetic, not a catalogue, so some sizes on the list aren’t made by anyone and others are made only for certain vehicles. Check availability with retailers.
What tolerance should I use?
That’s your choice and the vehicle maker’s. The tolerance just filters the list. Many people start within about 1–3% of the original overall diameter, but there’s no universal safe threshold; the vehicle’s approved sizes, load index and speed rating come first.
Why limit the width?
Very narrow or very wide sizes for a given wheel are usually impractical: each tire size is approved for a range of rim widths, and the width also has to clear the suspension and bodywork. Setting a width range keeps the list to realistic candidates.
What should I do with a size I like?
Open it in the 3D fitment studio to see how it sits on your wheel, then check that it’s made in a load index and speed rating that meets your vehicle’s placard, and that your wheel width is in its approved range.
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