Tire Size Comparison
Compare two tire sizes side by side to see the difference in overall diameter, sidewall, circumference, and speedometer reading. A fast tire size comparison before you change setups or go plus-size.
Comparison
Size Comparison
Tire A vs Tire B — drawn to scale, same center.
Reading a tire size comparison
The bigger the difference in overall diameter, the more your speedometer, ride height, and gearing change. A taller tire makes the speedometer read slower than your true speed; a shorter tire reads faster. Keeping a new size within roughly 3% of the original keeps your speedometer accurate.
Use this tire size comparison to plan a plus-size or a wider setup, then check fit with our wheel fitment calculator and size a single tire with the tire size calculator.
Common size swaps, compared
Most tire size comparison questions are about one swap: the size on the door sticker against the size you want next. Below are 30 common swaps, from plus-one wheel upgrades on cars to bigger all-terrains on trucks, worked out with the same math as the tool above. 18 of them stay inside the usual 3% rule.
- Diameter = wheel diameter + 2 × (width × aspect ratio ÷ 100) ÷ 25.4. Flotation sizes such as 33x12.50R20 give the diameter directly.
- Difference = new diameter − old diameter, and as a percent of the old diameter.
- True speed at 60 = your real speed when the speedometer shows 60 mph: 60 × new diameter ÷ old diameter.
| Swap | Diameter (in) | Difference | Width change | True speed at 60 | Verdict |
|---|---|---|---|---|---|
| 205/55R16 → 225/45R17 | 24.88 → 24.97 | +0.09 in (+0.4%) | +20 mm | 60.2 mph | Within 3% — speedometer stays close to true; check clearance for the extra width |
| 195/65R15 → 205/55R16 | 24.98 → 24.88 | -0.10 in (-0.4%) | +10 mm | 59.8 mph | Within 3% — speedometer stays close to true |
| 225/45R17 → 225/40R18 | 24.97 → 25.09 | +0.11 in (+0.5%) | 0 mm | 60.3 mph | Within 3% — speedometer stays close to true |
| 225/45R17 → 235/40R18 | 24.97 → 25.40 | +0.43 in (+1.7%) | +10 mm | 61.0 mph | Within 3% — speedometer stays close to true |
| 225/40R18 → 235/35R19 | 25.09 → 25.48 | +0.39 in (+1.6%) | +10 mm | 60.9 mph | Within 3% — speedometer stays close to true |
| 245/40R18 → 255/35R19 | 25.72 → 26.03 | +0.31 in (+1.2%) | +10 mm | 60.7 mph | Within 3% — speedometer stays close to true |
| 245/40R18 → 245/45R18 | 25.72 → 26.68 | +0.96 in (+3.8%) | 0 mm | 62.3 mph | Over 3% taller — recalibrate the speedometer and check clearance |
| 235/45R18 → 245/40R19 | 26.33 → 26.72 | +0.39 in (+1.5%) | +10 mm | 60.9 mph | Within 3% — speedometer stays close to true |
| 255/35R19 → 275/35R19 | 26.03 → 26.58 | +0.55 in (+2.1%) | +20 mm | 61.3 mph | Within 3% — speedometer stays close to true; check clearance for the extra width |
| 245/45R19 → 245/40R20 | 27.68 → 27.72 | +0.04 in (+0.1%) | 0 mm | 60.1 mph | Within 3% — speedometer stays close to true |
| 225/65R17 → 235/65R17 | 28.52 → 29.03 | +0.51 in (+1.8%) | +10 mm | 61.1 mph | Within 3% — speedometer stays close to true |
| 235/65R17 → 235/55R19 | 29.03 → 29.18 | +0.15 in (+0.5%) | 0 mm | 60.3 mph | Within 3% — speedometer stays close to true |
| 235/55R19 → 255/50R20 | 29.18 → 30.04 | +0.86 in (+3.0%) | +20 mm | 61.8 mph | Within 3% — speedometer stays close to true; check clearance for the extra width |
| 255/55R20 → 275/55R20 | 31.04 → 31.91 | +0.87 in (+2.8%) | +20 mm | 61.7 mph | Within 3% — speedometer stays close to true; check clearance for the extra width |
| 245/70R17 → 265/70R17 | 30.50 → 31.61 | +1.10 in (+3.6%) | +20 mm | 62.2 mph | Over 3% taller — recalibrate the speedometer and check clearance |
| 265/70R17 → 285/70R17 | 31.61 → 32.71 | +1.10 in (+3.5%) | +20 mm | 62.1 mph | Over 3% taller — recalibrate the speedometer and check clearance |
| 265/70R17 → 285/75R17 | 31.61 → 33.83 | +2.22 in (+7.0%) | +20 mm | 64.2 mph | Over 3% taller — recalibrate the speedometer and check clearance |
| 285/70R17 → 315/70R17 | 32.71 → 34.36 | +1.65 in (+5.1%) | +30 mm | 63.0 mph | Over 3% taller — recalibrate the speedometer and check clearance |
| 245/75R16 → 265/75R16 | 30.47 → 31.65 | +1.18 in (+3.9%) | +20 mm | 62.3 mph | Over 3% taller — recalibrate the speedometer and check clearance |
| 265/70R16 → 265/75R16 | 30.61 → 31.65 | +1.04 in (+3.4%) | 0 mm | 62.0 mph | Over 3% taller — recalibrate the speedometer and check clearance |
| 265/75R16 → 285/75R16 | 31.65 → 32.83 | +1.18 in (+3.7%) | +20 mm | 62.2 mph | Over 3% taller — recalibrate the speedometer and check clearance |
| 265/65R18 → 275/70R18 | 31.56 → 33.16 | +1.59 in (+5.1%) | +10 mm | 63.0 mph | Over 3% taller — recalibrate the speedometer and check clearance |
| 255/70R18 → 275/70R18 | 32.06 → 33.16 | +1.10 in (+3.4%) | +20 mm | 62.1 mph | Over 3% taller — recalibrate the speedometer and check clearance |
| 265/70R18 → 275/70R18 | 32.61 → 33.16 | +0.55 in (+1.7%) | +10 mm | 61.0 mph | Within 3% — speedometer stays close to true |
| 275/65R18 → 285/65R18 | 32.07 → 32.59 | +0.51 in (+1.6%) | +10 mm | 61.0 mph | Within 3% — speedometer stays close to true |
| 275/55R20 → 275/60R20 | 31.91 → 32.99 | +1.08 in (+3.4%) | 0 mm | 62.0 mph | Over 3% taller — recalibrate the speedometer and check clearance |
| 275/55R20 → 285/55R20 | 31.91 → 32.34 | +0.43 in (+1.4%) | +10 mm | 60.8 mph | Within 3% — speedometer stays close to true |
| 275/60R20 → 275/65R20 | 32.99 → 34.07 | +1.08 in (+3.3%) | 0 mm | 62.0 mph | Over 3% taller — recalibrate the speedometer and check clearance |
| 275/60R20 → 33x12.50R20 | 32.99 → 33.00 | +0.01 in (0.0%) | +43 mm | 60.0 mph | Within 3% — speedometer stays close to true; check clearance for the extra width |
| 275/65R20 → 35x12.50R20 | 34.07 → 35.00 | +0.93 in (+2.7%) | +43 mm | 61.6 mph | Within 3% — speedometer stays close to true; check clearance for the extra width |
The 3% rule is a speedometer guide, not a fit guarantee. Taller and wider tires can still rub on some vehicles, so check clearance with the wheel fitment calculator before you buy.
Want the common sizes for each wheel diameter in one place? See the tire size chart on our calculator page, or size a single tire with the tire size calculator.