Free tool
Tire size calculator & comparison
Compare two tire sizes side by side. See exactly how diameter, width, speedometer reading and ground clearance change before you upsize — in metric or inch sizes.
265/70R17 or 33x12.50R17.
265/70R17 → 285/70R18
Noticeable — recalibrate the speedo, check clearance
| Spec | Current | New | Difference |
|---|---|---|---|
| Overall diameter | 31.61" | 33.71" | +2.10" |
| Section width | 10.43" | 11.22" | +0.79" |
| Sidewall height | 7.30" | 7.85" | +0.55" |
| Circumference | 99.29" | 105.90" | +6.60" |
| Revolutions / mile | 638 | 598 | −40 |
Calculated from the size specs — real mounted diameter varies a little by brand, load and pressure. Always check clearance on your own truck before fitting.
How to read a tire size
Two formats, same tire. Here's what each number means.
Tread width
The width of the tread in millimetres, across the tire.
Aspect ratio
Sidewall height as a percent of width — a lower number is a shorter sidewall.
Rim diameter
R is radial; 17 is the wheel diameter in inches the tire mounts to.
Inch sizes
Flotation sizes like 33x12.50R17 give overall diameter × width × rim, all in inches.
Truck tire size chart: metric to inches
Common pickup tire sizes converted to inches — overall height, tread width and sidewall — so you can see what a metric size really measures. Click any size to compare it against your stock tire.
| Metric size | Height | Width | Sidewall | ≈ Inch size | Revs / mile |
|---|---|---|---|---|---|
| 245/75R16 | 30.5" | 9.6" | 7.2" | 30.5x9.6R16 | 662 |
| 265/75R16 | 31.6" | 10.4" | 7.8" | 31.6x10.4R16 | 637 |
| 285/75R16 | 32.8" | 11.2" | 8.4" | 32.8x11.2R16 | 614 |
| 315/75R16 | 34.6" | 12.4" | 9.3" | 34.6x12.4R16 | 583 |
| 245/70R17 | 30.5" | 9.6" | 6.8" | 30.5x9.6R17 | 661 |
| 265/70R17 | 31.6" | 10.4" | 7.3" | 31.6x10.4R17 | 638 |
| 275/70R17 | 32.2" | 10.8" | 7.6" | 32.2x10.8R17 | 627 |
| 285/70R17 | 32.7" | 11.2" | 7.9" | 32.7x11.2R17 | 617 |
| 285/75R17 | 33.8" | 11.2" | 8.4" | 33.8x11.2R17 | 596 |
| 315/70R17 | 34.4" | 12.4" | 8.7" | 34.4x12.4R17 | 587 |
| 265/65R18 | 31.6" | 10.4" | 6.8" | 31.6x10.4R18 | 639 |
| 275/65R18 | 32.1" | 10.8" | 7.0" | 32.1x10.8R18 | 629 |
| 265/70R18 | 32.6" | 10.4" | 7.3" | 32.6x10.4R18 | 619 |
| 275/70R18 | 33.2" | 10.8" | 7.6" | 33.2x10.8R18 | 608 |
| 285/65R18 | 32.6" | 11.2" | 7.3" | 32.6x11.2R18 | 619 |
| 295/70R18 | 34.3" | 11.6" | 8.1" | 34.3x11.6R18 | 589 |
| 325/65R18 | 34.6" | 12.8" | 8.3" | 34.6x12.8R18 | 582 |
| 275/55R20 | 31.9" | 10.8" | 6.0" | 31.9x10.8R2 | 632 |
| 285/55R20 | 32.3" | 11.2" | 6.2" | 32.3x11.2R2 | 624 |
| 275/60R20 | 33.0" | 10.8" | 6.5" | 33.0x10.8R2 | 611 |
| 295/60R20 | 33.9" | 11.6" | 7.0" | 33.9x11.6R2 | 594 |
| 275/65R20 | 34.1" | 10.8" | 7.0" | 34.1x10.8R2 | 592 |
| 285/65R20 | 34.6" | 11.2" | 7.3" | 34.6x11.2R2 | 583 |
| 325/60R20 | 35.4" | 12.8" | 7.7" | 35.4x12.8R2 | 570 |
| 285/45R22 | 32.1" | 11.2" | 5.0" | 32.1x11.2R22 | 628 |
Heights are calculated from the size code. Real mounted height runs a little shorter — usually a few tenths of an inch — and varies by brand, tread depth and inflation.
Speedometer error with bigger tires
A taller tire covers more ground per turn, so the speedometer reads low. True speed is the indicated speed multiplied by the new diameter over the old one. Find your percentage — the calculator above gives it for your exact sizes.
| Tire taller by | Shows 30 mph | Shows 45 mph | Shows 60 mph | Shows 75 mph |
|---|---|---|---|---|
| +3% | 30.9 mph | 46.4 mph | 61.8 mph | 77.3 mph |
| +5% | 31.5 mph | 47.3 mph | 63.0 mph | 78.8 mph |
| +8% | 32.4 mph | 48.6 mph | 64.8 mph | 81.0 mph |
| +10% | 33.0 mph | 49.5 mph | 66.0 mph | 82.5 mph |
| +12% | 33.6 mph | 50.4 mph | 67.2 mph | 84.0 mph |
| +15% | 34.5 mph | 51.8 mph | 69.0 mph | 86.3 mph |
Example: stock 265/70R17 (31.6") to 285/75R17 (33.8") is about 7% taller, so an indicated 60 mph is really about 64. Odometer mileage under-reads by the same percentage.
Plus sizing: a bigger wheel without a taller tire
Going up in wheel size while keeping the same overall height means a lower aspect ratio — less sidewall, more wheel. Here is the classic half-ton step-up from a 17-inch stock tire, with each size kept within about 2% of the original height.
| Size | Wheel | Height | Sidewall | vs stock |
|---|---|---|---|---|
| 265/70R17 | 17" | 31.6" | 7.3" | — |
| 265/65R18 | 18" | 31.6" | 6.8" | −0.1% |
| 275/55R20 | 2" | 31.9" | 6.0" | +1.0% |
| 285/45R22 | 22" | 32.1" | 5.0" | +1.6% |
The trade-off is the sidewall: from 7.3 inches on the 17 down to about 5 on the 22. A shorter sidewall sharpens steering but rides harder, protects the wheel less on potholes and trails, and costs more to replace. For a truck that works or goes off-road, the stock-size wheel with the taller sidewall is usually the better tire.
Tire sizes — frequently asked
How do I read a tire size like 265/70R17?
265 is the tread width in millimetres. 70 is the aspect ratio — the sidewall height as a percentage of the width (so 70% of 265 mm). R means radial construction, and 17 is the wheel (rim) diameter in inches. A flotation size like 33x12.50R17 instead reads as overall diameter (33"), width (12.5") and rim (17").
Will bigger tires mess up my speedometer?
Yes. Your speedometer is calibrated for the stock tire diameter. A taller tire travels further per revolution, so the speedo reads low — you're actually going faster than it shows. This calculator gives the true speed at an indicated 60 mph so you can see the error and recalibrate if needed.
How much bigger can I go without a lift?
As a rough guide, most trucks accept a tire about 3–5% taller than stock without rubbing. Beyond roughly 15% you usually need a level or lift kit and possibly trimming. Always check your specific truck — fender clearance and offset vary.
Does a taller tire change my gearing?
Yes — a taller tire effectively raises your gearing (fewer revolutions per mile), which can dull acceleration and drop your effective final drive. Many people re-gear the axles after a big tire jump to restore performance. The revs-per-mile difference here shows the size of that change.
What does a wider tire affect?
Width changes grip and stance but also rubbing risk on the inner fender and suspension at full lock or compression. Going wider often needs a different wheel offset/backspacing to keep the tire clear.
What size is a 33-inch tire in metric?
There is no single metric 33. The metric sizes that measure close to 33 inches tall are 285/75R16 (32.8"), 285/70R17 (32.7"), 265/70R18 (32.6"), 275/70R18 (33.2"), 285/65R18 (32.6") and 275/60R20 (33.0"). Pick the one that matches your wheel diameter — the last number — and then check the width against your fender and offset. Inch-sized tires like 33x12.50R17 are labelled by their nominal height, and the real mounted height often runs half an inch shorter.
What size is a 35-inch tire in metric?
Metric tires sold as 35s measure roughly 34.4 to 35.4 inches: 315/75R16 (34.6"), 315/70R17 (34.4"), 325/65R18 (34.6"), 285/65R20 (34.6") and 325/60R20 (35.4"). On most half-ton pickups a 35 needs a level or lift kit, and often a different wheel offset and some trimming — run your setup through the lift kit calculator before you buy.
How do you calculate tire diameter from the size?
Multiply the width by the aspect ratio to get the sidewall height in millimetres, double it (there is a sidewall above and below the wheel), divide by 25.4 to convert to inches, then add the rim diameter. For 265/70R17: 265 × 0.70 = 185.5 mm sidewall, × 2 = 371 mm, ÷ 25.4 = 14.6 inches, + 17 = 31.6 inches tall.
How much bigger can a replacement tire be?
The usual plus-sizing guideline is to keep the new overall diameter within about 3% of stock. That keeps speedometer error small, stays inside the clearance the factory designed for and keeps ABS and stability control reading wheel speed close to what they expect. Bigger jumps are common on lifted trucks, but then you are into recalibrating the speedometer and often re-gearing.
