How to compare tire sizes
- Enter your current tire size. It's on the tire sidewall and on the placard in the driver's door jamb.
- Enter the new tire size you're considering. Metric (285/70R17), LT (LT285/75R16) and flotation (35x12.50R17) sizes all work.
- Read the height difference in percent at the top, then the side-by-side table: diameter, section width, sidewall, circumference and revolutions per mile.
- Check the speedometer table to see your true speed at common readings with the new tires.
Example: 265/70R17 vs 285/70R17
| Measurement | 265/70R17 | 285/70R17 | Difference |
|---|---|---|---|
| Diameter | 31.61 in | 32.71 in | +1.10 in (+3.5%) |
| Width | 10.43 in | 11.22 in | +0.79 in (+7.5%) |
| Sidewall | 7.30 in | 7.85 in | +0.55 in (+7.5%) |
| Ride height | Raised at the axle by half the height difference | +0.55 in | |
The 285 is +3.5% taller, just over the 3% guideline, so at an indicated 60 mph you'd actually be doing 62.1 mph.
How much bigger can you go? The 3% rule
Tire shops generally recommend keeping the new overall diameter within ±3% of the original. Inside that range the speedometer error is small (under 2 mph at 60), ABS and traction control work as designed, and the tire usually clears the body and suspension. Going bigger is common on trucks and off-road builds, but plan for:
- Speedometer and odometer error: they read low with taller tires. Recalibrate with a programmer or at the dealer.
- Gearing: taller tires act like a taller (numerically lower) axle ratio, so acceleration and towing suffer; big jumps often need re-gearing.
- Clearance: check at full steering lock and full suspension compression. A lift, leveling kit or different wheel offset may be needed.
- Fuel economy: heavier, wider tires usually cost some mpg, and your trip computer will over-report mileage until recalibrated.
Common tire upgrades compared
| From | To | Height | Width | At 60 mph |
|---|---|---|---|---|
| 225/65R17 | 235/65R17 | +0.51 in (+1.8%) | +0.39 in | 61.1 mph |
| 245/75R16 | 265/75R16 | +1.18 in (+3.9%) | +0.79 in | 62.3 mph |
| 265/70R17 | 285/70R17 | +1.10 in (+3.5%) | +0.79 in | 62.1 mph |
| 265/70R17 | 285/75R17 | +2.22 in (+7.0%) | +0.79 in | 64.2 mph |
| 275/65R18 | 285/65R18 | +0.51 in (+1.6%) | +0.39 in | 61.0 mph |
| 275/55R20 | 275/60R20 | +1.08 in (+3.4%) | 0.00 in | 62.0 mph |
| 275/60R20 | 295/60R20 | +0.94 in (+2.9%) | +0.79 in | 61.7 mph |
| 265/70R17 | 35x12.50R17 | +3.39 in (+10.7%) | +2.07 in | 66.4 mph |
Plus sizing: bigger wheels, same overall height
Moving to a larger wheel ("plus one") needs a shorter sidewall to keep the height. 205/55R16 → 225/45R17 changes the height by only +0.4% (+0.09 in) while the wheel grows an inch and the tire gets 0.79 in wider. The tire size calculator lists every equivalent size within 3% for your tire.
Related tire and wheel tools
- Tire size calculator: full dimensions of one size, a tire size chart, and equivalent sizes.
- Speedometer calculator: true speed and odometer error after a tire or axle gear change.
- Wheel offset calculator: how far new wheels poke out or tuck in, and offset to backspacing.
Frequently asked questions
How much bigger is a 285/70R17 than a 265/70R17?
285/70R17 is 32.71 in tall and 11.22 in wide; 265/70R17 is 31.61 in and 10.43 in. So the 285 is 1.10 in taller (+3.5%), 0.79 in wider, and raises the vehicle 0.55 in at the axle.
What is the 3% rule for tire sizes?
Most tire shops and manufacturers recommend keeping a replacement size within about 3% of the original overall diameter (some allow up to 3% smaller and a little more larger). Within that range the speedometer, ABS and stability control still read close to correct and the tire usually fits. Beyond it, check clearance and plan to recalibrate the speedometer.
What is the difference between a 265 and a 275 tire?
10 mm of section width, which is about 0.39 in. With the same aspect ratio the sidewall also grows (because it's a percentage of the width), so 275/70R17 is 0.55 in taller than 265/70R17 (+1.7%).
Do bigger tires affect the speedometer?
Yes. A taller tire covers more ground per turn, so the speedometer reads low. With 285/70R17 instead of 265/70R17, an indicated 60 mph is really 62.1 mph. Use the speedometer calculator for a full table, including gear ratio changes.
Does a wider tire make it taller?
Usually, yes. The aspect ratio is a percentage of the width, so at the same aspect ratio a wider tire has a taller sidewall. To go wider without getting taller, drop the aspect ratio: for example 225/65R17 → 245/60R17 keeps the height almost the same.
Can I compare a metric size with a flotation size like 35x12.50R17?
Yes. Enter each size as written, for example 265/70R17 and 35x12.50R17, and the calculator converts both to inches and millimeters before comparing them.
Will a bigger tire fit my vehicle?
The numbers tell you how much taller and wider the tire is, and how much the ride height changes, but fit also depends on your wheel width and offset, suspension and body. Check turning clearance at full lock and with the suspension compressed, or ask a tire shop about your exact vehicle. A wheel offset calculator shows how new wheels change clearance.
Is my data saved or sent anywhere?
Your entries are saved only in your own browser so they are there next time. Nothing is sent to our servers.