This size is common on full-size trucks and SUVs in the U.S. Below, you’ll find the tire dimensions, similar sizes, fitment tips, and how to pick the right set.
275/65R18 Tire Size in Inches and Millimeters
| Measurement | Inches | Millimeters |
|---|---|---|
| Overall diameter | 32.1 | 815 |
| Section width | 10.8 | 275 |
| Sidewall height | 7.0 | 179 |
| Rim diameter | 18 | 457 |
| Circumference | 100.8 | 2,560 |
| Revolutions per mile | 629 | – |
What Each Number in 275/65R18 Means
- 275 is the section width in millimeters. It is measured from one sidewall to the other.
- 65 is the aspect ratio. The sidewall is 65% as tall as the tire is wide.
- R means radial construction. Almost all modern tires are radial.
- 18 is the wheel diameter in inches.
How to Convert 275/65R18 to Inches
You can do the math yourself in three steps.
- Width: 275 ÷ 25.4 = 10.83 inches.
- Sidewall: 275 × 0.65 = 178.75 mm, which is 7.04 inches.
- Diameter: (7.04 × 2) + 18 = 32.08 inches.
Some charts show 32.07 and others show 32.1. The gap is tiny and won’t affect real driving.
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Load Index, Speed Rating, and LT vs P
A 116T tire carries up to 2,756 lbs and is rated to 118 mph. A 123S tire carries up to 3,415 lbs and is rated to 112 mph.
A “P” before the size means passenger tire. “LT” means light truck tire, built for heavier loads.
What Wheel Width Fits 275/65R18?
Most makers approve about 7.5 to 9.5 inches of wheel width for passenger versions. LT versions usually allow about 7.5 to 9 inches. Check the tire maker’s chart for your exact model.
275/65R18 vs Similar Tire Sizes
275/65R18 vs 265/65R18 and 265/70R18
A 275 tire is about 10 mm (0.4 inch) wider. That small change rarely causes fitment trouble.
The 265/65R18 is about 1.6% shorter. The 265/70R18 is about 1.7% taller.
275/65R18 vs 285/75R18 and 275/70R18
The 285/75R18 is a big jump. It stands about 34.8 inches tall, which is 8.6% taller. Its sidewall is also about 20% taller.
The 275/70R18 is about 33.2 inches tall, or 3.4% taller. It may need a leveling kit on some trucks.
275/65R18 Equivalent Sizes and the 3% Rule
| Size | Diameter (in) | Difference |
|---|---|---|
| 265/65R18 | 31.6 | −1.6% |
| 265/70R18 | 32.6 | +1.7% |
| 285/65R18 | 32.6 | +1.6% |
| 275/70R17 | 32.2 | +0.2% |
| 275/60R20 | 33.0 | +2.9% |
| 275/70R18 | 33.2 | +3.4% |
| 285/75R18 | 34.8 | +8.6% |
If you switch to a 17-inch wheel, the 275/70R17 is the closest match.
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275/65R18 Fitment, Speedometer, and Performance Effects
Which Vehicles Use 275/65R18 Tires?
This size shows up on full-size pickups and large SUVs. It is common on trucks like the Ford F-150 and Toyota Tundra. It is also a popular upsize for the Toyota Tacoma.
Sizes change by trim and model year. Always check the tire placard on the driver’s door jamb first.
Speedometer Error
Your speedometer counts wheel turns, not true speed. A taller tire covers more ground per turn.
Here are two examples at 60 mph indicated:
- 275/70R18: you travel about 62.0 mph.
- 285/75R18: you travel about 65.1 mph.
Your odometer reads low too. A speedometer recalibration fixes both.
Engine RPM and Fuel Economy
You can estimate engine RPM with this formula:
RPM = revolutions per mile × mph ÷ 60 × axle ratio
At 65 mph with a 3.73 axle ratio: 629 × 65 ÷ 60 × 3.73 ≈ 2,542 RPM. This assumes a 1:1 top gear. Trucks with overdrive run lower.
Heavier tires and aggressive tread add rolling resistance. Federal estimates show proper tire pressure can improve mileage by up to 3%.
Rubbing, Lifts, TPMS, and Snow Chains
- Rubbing: wider or taller tires may rub on fenders or control arms at full turn. The wheel’s offset matters here.
- TPMS: U.S. vehicles built since the 2007 model year have a tire pressure monitoring system. A shop may need to reset it after a swap.
- Snow chains: some makers ban chains on certain sizes because of tight clearance. Check your owner’s manual.
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How to Choose the Best 275/65R18 Tires
Pick the Tire Type by Driving Style
- Daily commuting: choose a highway or all-season tire.
- Mixed road and trail: choose an all-terrain tire.
- Heavy off-roading: choose a mud-terrain tire.
- Snow and ice: choose a winter tire or one with the 3-peak mountain snowflake symbol.
SL vs XL vs E Load Range
SL means standard load. XL means extra load. Load range E is a 10-ply rated LT tire for towing and hauling.
E-rated tires are tougher but heavier. They often ride stiffer and may cost more fuel.
Price, Treadwear, and Buying Checklist
Prices often run from about $120 to over $400 per tire. Mileage warranties commonly range from 40,000 to 70,000 miles.
Before you buy, check:
- The size and load index on your door placard
- The DOT date code. The last four digits show the week and year made.
- The treadwear warranty and return policy
Many automakers suggest replacing tires around six years old, even with deep tread.
Tire Care Tips
- Use the door-jamb pressure, not the number on the sidewall.
- Tires lose about 1 psi per month and about 1 psi per 10°F drop in temperature.
- Rotate every 5,000 to 7,500 miles.
- Get an alignment check if wear looks uneven.
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FAQ’s About 275/65R18 Tire Size
What are the exact dimensions of a 275/65R18 tire in inches?
A 275/65R18 tire is about 32.1 inches in overall diameter, 10.8 inches wide, and has a 7-inch sidewall. It fits an 18-inch rim.
Is 275/65R18 the same as a 33-inch tire?
No. It measures about 32.1 inches. A true 33-inch tire, like the 33×12.50R18, is about 0.9 inch taller and much wider.
Can I replace 265 series tires with 275 series tires?
Usually, yes. A 275 tire is about 10 mm wider than a 265. That is a small change. Check wheel width and clearance first.
Does 275/65R18 affect fuel economy?
It can. Heavier or taller tires increase rolling resistance. The effect is usually small and shows up most at highway speeds.
How does 275/65R18 affect my speedometer?
If it is your factory size, nothing changes. If you move up from a smaller size, your actual speed will be higher than the display. A recalibration fixes it.
What wheel width fits 275/65R18?
Most makers approve about 7.5 to 9.5 inches for passenger tires. LT tires usually allow 7.5 to 9 inches.
I’m Richard Hayes, a content researcher and writer at TireMeasurements.com, specializing in measurements, tire measurements, tire sizing, wheel fitment, and related automotive topics.
