Tire size comparison
295/70R18 vs 33x12.50R18
33x12.50R18 is −3.7% shorter than 295/70R18: 33.0 in vs 34.3 in (−1.26 in), and 0.9 in wider. With 33x12.50R18 on a vehicle set up for 295/70R18, the speedometer shows 60 mph at an actual 57.8 mph. That is more than the ±3% difference many shops use as a rule of thumb, so check carefully before switching.
Set up for: going smaller (33x12.50R18 instead of 295/70R18) · Different situation?
Your current size
e.g. 265/70R17, 2657017 or 33x12.50R20
Where do I find my size?
It's on the tire sidewall, e.g. P265/70R17 115T, and on the tire placard sticker on the driver's door jamb (also in the owner's manual). The placard shows the size the vehicle came with; the sidewall shows what is fitted now. If they differ, use the placard as your starting point. Digits are enough here: 2657017 or 33125020.
Size you're considering
295/70R18 vs 33x12.50R18: full comparison
| 295/70R18 | 33x12.50R18 | Difference | |
|---|---|---|---|
| Overall diameter | 34.26 in | 33.00 in | −1.26 in (−3.7%) |
| Width | 11.61 in | 12.50 in | +0.89 in (+7.6%) |
| Sidewall height | 8.13 in | 7.50 in | −0.63 in |
| Circumference | 107.6 in | 103.7 in | −4.0 in |
| Revs per mile (nominal) | 589 | 611 | +22 |
| Wheel diameter | 18 in | 18 in | ±0 in |
| Diameter in mm | 870 | 838 | −32 mm |
Speedometer difference
Your speedometer is calibrated for 295/70R18. Fitted with 33x12.50R18, the actual speed is the reading × 33.00 ÷ 34.26.
| Speedometer shows | Actual speed | Difference |
|---|---|---|
| 20 mph | 19.3 mph | −0.7 mph |
| 30 mph | 28.9 mph | −1.1 mph |
| 45 mph | 43.3 mph | −1.7 mph |
| 55 mph | 53.0 mph | −2.0 mph |
| 60 mph | 57.8 mph | −2.2 mph |
| 70 mph | 67.4 mph | −2.6 mph |
| 80 mph | 77.1 mph | −2.9 mph |
Real tires: published diameters
295/70R18: 34.29–34.57 in published by 5 makers; 33x12.50R18: 32.5–33 in published by 5 makers. Calculated figures assume a nominal tire; the exact difference between two specific tires depends on their models.
More about each size: 295/70R18 · 33x12.50R18
Related comparisons
FAQ
Which is bigger, 295/70R18 or 33x12.50R18?
33x12.50R18 is −3.7% shorter than 295/70R18: 33.0 in vs 34.3 in (−1.26 in).
How much will my speedometer be off with 33x12.50R18 instead of 295/70R18?
The speedometer is calibrated for 295/70R18. With 33x12.50R18 it shows 60 mph when you are doing 57.8 mph, and 70 mph at 67.4 mph (−3.7%). Your speedometer also has its own factory tolerance.
Can I replace 295/70R18 with 33x12.50R18?
The diameter difference is −3.7%. Whether it fits depends on things this calculation can't see: wheel width and offset, clearance at full lock and over bumps, load index and speed rating, and your vehicle maker's approval. Check your door-jamb placard and owner's manual and ask a tire professional.