Plus Sizing Calculator
Plus sizing means fitting a larger rim with a lower-profile tire so the overall diameter stays about the same. Plus one is one inch more rim, for example 205/55R16 to 225/45R17. Enter your size and the new rim below for sizes within 3% of your current diameter, closest first.
Find plus sizes
The calculator needs JavaScript. The formulas and tables on this page work without it: sidewall = width × aspect ratio ÷ 100, and diameter = rim × 25.4 + 2 × sidewall (in mm).
Plus sizes
How to use it
- Enter your current tire size.
- Choose the new rim diameter.
- Read the sizes within 3% of your current diameter, closest first.
- Check availability, load index and fit with a tire shop.
Typical plus sizing examples
| Size | Diameter (in) | Diameter (mm) | Width (in) | Sidewall | Revs per mile |
|---|---|---|---|---|---|
| 205/55R16 | 24.9 in | 632 mm | 8.1 in | 113 mm | 811 |
| 215/50R17 | 25.5 in | 647 mm | 8.5 in | 108 mm | 792 |
| 225/45R17 | 25.0 in | 634 mm | 8.9 in | 101 mm | 808 |
| 225/40R18 | 25.1 in | 637 mm | 8.9 in | 90 mm | 804 |
| 235/40R18 | 25.4 in | 645 mm | 9.3 in | 94 mm | 794 |
| 225/35R19 | 25.2 in | 640 mm | 8.9 in | 79 mm | 800 |
| 235/35R19 | 25.5 in | 647 mm | 9.3 in | 82 mm | 792 |
What changes with plus sizing
- Lower sidewall: usually sharper steering response and a firmer ride.
- Wider tire: may need a wider rim and more space in the wheel arch.
- Wheel and tire weight: can go up or down depending on the wheel and tire chosen.
Load index and speed symbol
Your vehicle’s tire placard and owner’s manual give the load index and speed symbol specified for your vehicle. Keep at least those values, and check that the new size suits your wheels. Always check your vehicle owner’s manual, the tire placard in the door jamb, or a tire shop before changing size.
How the list is made
The tool tries every standard width from 145 to 355 mm (10 mm steps) and aspect ratio from 25 to 85% (5% steps) on the new rim, keeps widths from 10 mm narrower to 40 mm wider than your current tire, and lists those within 3% of your current diameter. Not every combination is made.
Frequently asked questions
What is plus sizing?
Fitting a wheel with a larger diameter and a tire with a lower sidewall, so that the overall diameter stays close to the original. Plus one adds one inch to the rim, plus two adds two.
What is plus one for 205/55R16?
Plus one options include 225/45R17, which is within 0.5% of the original diameter, and 215/50R17, which is about 2.4% larger. Check that the width suits your new wheels and that the load index is enough.
Why keep the same overall diameter?
So the speedometer, gearing, ground clearance and space in the wheel arch stay close to what the vehicle was set up for. The calculator lists sizes within 3%.
Does plus sizing affect ride comfort?
Usually the ride gets firmer because the lower sidewall flexes less. How much you notice depends on the tire model, the wheel, the tire pressure and the vehicle’s suspension.
Do I need a different load index?
Keep at least the load index and speed symbol given for your vehicle on the tire placard or in the manual. Low-profile sizes often come as XL versions to reach the same load.
Are all listed sizes available?
No. The list is calculated from standard steps. Many combinations are not made. A tire shop can tell you which are available and suit your vehicle.
Last updated: October 15, 2026