205/75R15 vs 305/30R20 tire size comparison
305/30R20 is 0.1 in (0.36%) taller than 205/75R15 and 3.9 in wider. They fit different wheels: 205/75R15 a 15-inch wheel and 305/30R20 a 20-inch wheel.
205/75R15 and 305/30R20 side by side
| Measurement | 205/75R15 | 305/30R20 | Difference | Difference % |
|---|---|---|---|---|
| Section width | 8.1 in (205 mm) | 12.0 in (305 mm) | +3.9 in (+100 mm) | +48.78% |
| Sidewall height | 6.1 in (154 mm) | 3.6 in (92 mm) | -2.5 in (-62 mm) | -40.49% |
| Wheel (rim) diameter | 15.0 in (381 mm) | 20.0 in (508 mm) | +5.0 in (+127 mm) | +33.33% |
| Overall diameter | 27.1 in (689 mm) | 27.2 in (691 mm) | +0.1 in (+2 mm) | +0.36% |
| Circumference | 85.2 in (2163 mm) | 85.5 in (2171 mm) | +0.3 in (+8 mm) | +0.36% |
| Revolutions per mile | 744 | 741 | -3 | -0.36% |
Differences are 305/30R20 minus 205/75R15; percentages are relative to 205/75R15. These are nominal design dimensions. Real tires vary by brand, tread depth, wheel width, load and pressure.
The overall diameter differs by 0.36%, which is within the common 3% rule of thumb.
The rule of thumb keeps a replacement size within about 3% of the original overall diameter. It covers diameter only. It is not a fit, load or safety check, because width, wheel diameter, load capacity and clearance matter too. Confirm any size change with your vehicle's owner's manual or a tire professional.
Speedometer difference
When the speedometer reads 60 mph on a vehicle built for 205/75R15, the actual speed on 305/30R20 is about 60.2 mph. When it reads 60 mph on a vehicle built for 305/30R20, the actual speed on 205/75R15 is about 59.8 mph. These figures assume the speedometer is accurate on the original size and use nominal dimensions, so treat them as estimates.
| Speedometer reads | Actual on 305/30R20 (built for 205/75R15) | Actual on 205/75R15 (built for 305/30R20) |
|---|---|---|
| 20 mph | 20.1 mph | 19.9 mph |
| 30 mph | 30.1 mph | 29.9 mph |
| 40 mph | 40.1 mph | 39.9 mph |
| 50 mph | 50.2 mph | 49.8 mph |
| 60 mph | 60.2 mph | 59.8 mph |
| 70 mph | 70.3 mph | 69.7 mph |
| 80 mph | 80.3 mph | 79.7 mph |
A common rule of thumb is to keep a replacement size within about 3% of the original overall diameter. Check the tire placard on the driver's door jamb and your owner's manual for the sizes your vehicle was built for. Confirm any size change with your vehicle's owner's manual or a tire professional.
Which vehicles use each size?
These vehicles list the size among their verified sizes, by trim. Open one to see all of its sizes.
305/30R20
- 2022 Acura NSX Type S(rear)
- 2021 Acura NSX NSX(rear)
- 2020 Acura NSX NSX(rear)
- 2026 Chevrolet Corvette Stingray(rear)
- 2025 Chevrolet Corvette Stingray 1LT(rear)
- 2025 Chevrolet Corvette Stingray 1LT w/ Z51 Performance Pkg.(rear)
- 2025 Chevrolet Corvette Stingray 2LT(rear)
- 2025 Chevrolet Corvette Stingray 2LT w/ Z51 Performance Pkg.(rear)
- 2025 Chevrolet Corvette Stingray 3LT(rear)
- 2025 Chevrolet Corvette Stingray 3LT w/ Z51 Performance Pkg.(rear)
Check it in the calculator
The calculator takes the same two sizes and shows the full comparison, or lets you swap either one for another size.
Open this comparison in the calculatorShop for 205/75R15 or 305/30R20 tires
Confirm the size on your tire sidewall or door placard first. These links open each store's own search; prices and stock are on their sites.
205/75R15
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Other comparisons with 205/75R15
Side-by-side dimensions and speedometer difference for sizes close to 205/75R15 in overall diameter.
- 205/75R15 vs 235/60R16-0.01% shorter than 205/75R15
- 205/75R15 vs 215/60R17+0.19% taller than 205/75R15
- 205/75R15 vs 255/45R18-0.26% shorter than 205/75R15
- 205/75R15 vs 255/40R19-0.28% shorter than 205/75R15
- 205/75R15 vs 255/35R20-0.29% shorter than 205/75R15
Other comparisons with 305/30R20
Side-by-side dimensions and speedometer difference for sizes close to 305/30R20 in overall diameter.
- 235/50R18 vs 305/30R20+0.17% taller than 305/30R20
- 215/60R17 vs 305/30R20-0.17% shorter than 305/30R20
- 265/35R20 vs 305/30R20+0.36% taller than 305/30R20
- 235/60R16 vs 305/30R20-0.38% shorter than 305/30R20
- 215/55R18 vs 305/30R20+0.39% taller than 305/30R20
You might also need
- Digital tire pressure gauge (Amazon search, opens in a new tab)
Check your tire pressure against the number on your door placard.
- Portable tire inflator (Amazon search, opens in a new tab)
Top up a low tire at home without a trip to the gas station.
- Tire tread depth gauge (Amazon search, opens in a new tab)
Measure how much tread is left before you decide to replace.
- Lug wrench or torque wrench (Amazon search, opens in a new tab)
Useful for rotations and tire changes; follow the torque spec in your owner's manual.
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