# Tire size calculator

Enter your current size and the size you are thinking of. The table updates as you type.

## How much bigger can I go?

Keep the new overall diameter within about 3% of the original. Beyond that the speedometer and odometer read noticeably wrong, and ABS, traction control and automatic transmission shift points, which all use wheel speed, can be affected. Bigger tires can also rub the fender or suspension on full lock.

## How is it calculated?

1. Sidewall height = width x aspect ratio / 100 (in mm).
2. Overall diameter = rim diameter x 25.4 + 2 x sidewall height.
3. Circumference = π x diameter; revolutions per mile = 63,360 / circumference in inches.
4. Speedometer error = new diameter / old diameter: a 3% larger tire means the car is going about 61.8 mph when the speedometer shows 60.

## Frequently asked questions

### Will bigger tires make my speedometer wrong?

Yes. A taller tire covers more ground per turn, so the car goes faster than the speedometer shows. With a tire 3% taller, an indicated 60 mph is about 61.8 mph.

### Can I use a wider tire on the same wheel?

Often one size wider (10 mm) is fine, but each tire size has an approved wheel-width range set by the tire industry. Check the tire maker's spec sheet and make sure it clears the suspension.

### Do I need to change all four tires if I change size?

Yes on all-wheel-drive cars, and strongly recommended on every car. Mixing diameters front to rear can strain an AWD system and confuse ABS and stability control.

## Popular sizes

- [175/65R14](https://diagxcar.com/tools/tire-size/175-65r14)
- [185/65R15](https://diagxcar.com/tools/tire-size/185-65r15)
- [195/60R15](https://diagxcar.com/tools/tire-size/195-60r15)
- [195/65R15](https://diagxcar.com/tools/tire-size/195-65r15)
- [205/55R16](https://diagxcar.com/tools/tire-size/205-55r16)
- [205/60R16](https://diagxcar.com/tools/tire-size/205-60r16)
- [205/65R16](https://diagxcar.com/tools/tire-size/205-65r16)
- [215/55R16](https://diagxcar.com/tools/tire-size/215-55r16)
- [215/60R16](https://diagxcar.com/tools/tire-size/215-60r16)
- [215/65R16](https://diagxcar.com/tools/tire-size/215-65r16)
- [245/75R16](https://diagxcar.com/tools/tire-size/245-75r16)
- [265/75R16](https://diagxcar.com/tools/tire-size/265-75r16)

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Source page: https://diagxcar.com/tools/tire-size-calculator
General information, not a substitute for a qualified mechanic.