Tire Size Calculator & Comparison
Compare tire sizes. See the difference before you buy — diameter, width and the speedometer change, drawn to scale in plain numbers. Free, no signup, calculated in your browser.
Current tire on your vehicle now
New tire you are considering
Full comparison
| Measurement | 265/70R17 | 285/70R17 |
|---|---|---|
| Overall diameter | 31.61" | 32.71" +1.1" (+3.49%) |
| Width | 10.43" | 11.22" +0.79" |
| Sidewall height | 7.3" | 7.85" +0.55" |
| Circumference | 99.3" | 102.8" +3.5" |
| Revolutions / mile | 638 | 617 -21 revs |
| Ride height change | — | +0.55" |
Speedometer effect
Assuming your speedometer was accurate on the current tire, here is what changes. Bigger tires make the speedometer read low — you travel faster than it shows.
| Speedometer shows | 20 mph | 30 mph | 40 mph | 50 mph | 60 mph | 70 mph | 80 mph |
|---|---|---|---|---|---|---|---|
| Actual speed | 20.7 | 31 | 41.4 | 51.7 | 62.1 | 72.4 | 82.8 |
What else changes
Odometer: it under-records by about 3.49%, the same error as the speedometer. When the clock shows 100,000 miles you have really covered about 103,500 miles — count service intervals and lease mileage by the real figure.
Gearing & feel: effectively 3.49% taller gearing. The truck pulls a touch lazier from a stop and works harder towing; at this size of change most drivers notice it mainly on hills or with a trailer.
Fuel economy: a taller, heavier tire usually costs a little fuel — through its weight, tread pattern and the taller gearing above. That part depends on the specific tire model, so no honest figure comes from the size code alone.
Before you buy: fitment checklist
- Wheel diameter: SAME RIM Both sizes have a 17" bead-seat diameter, so the wheel diameter matches and no new wheels are needed for diameter. That says nothing about wheel width — see the rim-width check below.
- Diameter change: DIAMETER Diameter changes 3.49% — beyond the ±3% rule of thumb installers commonly cite. Expect speedometer, gearing and clearance effects to matter. The ±3% figure is a guideline, not a safety standard.
- Clearance: WIDTH The new tire is 20 mm wider — check inner clearance at full steering lock and full suspension travel.
- Rim width: CHECK Confirm the new size's approved rim-width range (from the tire maker) includes your wheel's width.
- Load & speed: CHECK The new tire's load index and speed rating must meet or exceed your vehicle's placard (driver's door jamb).
- Warranty & inspection: NOTE Running a non-stock size can complicate warranty claims on related parts, and a few places check tire size at inspection. If either matters to you, check your vehicle's terms first.
This is a size comparison, not a fitment guarantee. Clearance depends on your vehicle's suspension, wheel offset and alignment — the checklist above covers what to verify.
Popular tire size comparisons
Popular sizes in inches
Questions drivers ask
How much taller is a 285/70R17 than a 265/70R17?
A 285/70R17 is 32.71" in diameter against 31.61" for the 265/70R17 — about 1.10" taller (+3.49%) and 0.79" wider. It raises ride height by roughly 0.55". Try it in the tool above.
Does a bigger tire make my speedometer wrong?
Yes. The speedometer counts wheel rotations, so a taller tire covers more ground per rotation than the gauge assumes. With a +3.49% diameter increase, an indicated 60 mph is really about 62.1 mph. The table above shows the correction at every speed.
What does 265/70R17 mean?
265 is the width in millimeters, 70 is the sidewall height as a percentage of the width (70%), and 17 is the wheel diameter in inches. The overall diameter works out to 31.61".
Can I put a different size on the same rims?
Only if the rim diameter matches and your wheel width is inside the new tire's approved rim-width range. Diameter changes within about ±3% are a common rule of thumb, but that is a guideline, not a safety standard — run through the checklist above before buying.
Are these the exact sizes of real tires?
These are nominal sizes from the standard formula every tire size is built on. A specific brand and model can measure a few tenths of an inch different, and a worn or loaded tire sits lower. Use these numbers to compare sizes, and the tire maker's spec sheet for one exact model.
Method and data notes: how every number here is calculated. Last verified November 12, 2026.