265/40R21 tire size
265/40R21 is a metric size: 29.3" tall, 10.4" wide, on a 21" rim — about a 29.5x10.50R21. The sidewall is 4.2" and the tire turns 687 times per mile.
265/40R21 specs
| Overall diameter (height) | 29.35" · 745 mm |
|---|---|
| Section width | 10.43" · 265 mm |
| Sidewall height | 4.17" · 106 mm (40% of width) |
| Rim diameter | 21" |
| Circumference | 92.19" · 2.342 m |
| Revolutions per mile | 687 (427 per km) |
| Inch (flotation) equivalent | 29.5x10.50R21 |
Equivalent sizes on a 21" rim
Sizes within ±5% of the overall diameter. Green rows are inside the usual ±3% limit for keeping the speedometer, ABS and gearing right; red rows are bigger changes that need clearance checks.
| Size | Diameter | Difference | Width | Speedo at 60 | |
|---|---|---|---|---|---|
| 275/35R21 common | 28.58" | -2.62% | +10 mm | 58.4 mph | compare → |
| 295/35R21 | 29.13" | -0.74% | +30 mm | 59.6 mph | compare → |
| 275/45R21 | 30.74" | +4.76% | +10 mm | 62.9 mph | compare → |
| 255/40R21 | 29.03" | -1.07% | -10 mm | 59.4 mph | compare → |
| 265/35R21 | 28.30" | -3.56% | 0 mm | 57.9 mph | compare → |
| 295/40R21 | 30.29" | +3.22% | +30 mm | 61.9 mph | compare → |
| 285/40R21 | 29.98" | +2.15% | +20 mm | 61.3 mph | compare → |
| 265/45R21 | 30.39" | +3.56% | 0 mm | 62.1 mph | compare → |
| 325/30R21 | 28.68" | -2.28% | +60 mm | 58.6 mph | compare → |
| 275/40R21 | 29.66" | +1.07% | +10 mm | 60.6 mph | compare → |
| 255/35R21 | 28.03" | -4.49% | -10 mm | 57.3 mph | compare → |
| 285/35R21 | 28.85" | -1.68% | +20 mm | 59.0 mph | compare → |
| 315/30R21 | 28.44" | -3.09% | +50 mm | 58.1 mph | compare → |
| 315/35R21 | 29.68" | +1.14% | +50 mm | 60.7 mph | compare → |
| 245/40R21 | 28.72" | -2.15% | -20 mm | 58.7 mph | compare → |
| 305/30R21 | 28.20" | -3.89% | +40 mm | 57.7 mph | compare → |
| 295/30R21 | 27.97" | -4.70% | +30 mm | 57.2 mph | compare → |
| 255/45R21 | 30.04" | +2.35% | -10 mm | 61.4 mph | compare → |
| 245/45R21 | 29.68" | +1.14% | -20 mm | 60.7 mph | compare → |
| 235/50R21 | 30.25" | +3.09% | -30 mm | 61.9 mph | calculate → |
| 355/25R21 | 27.99" | -4.63% | +90 mm | 57.2 mph | calculate → |
| 235/45R21 | 29.33" | -0.07% | -30 mm | 60.0 mph | calculate → |
| 305/35R21 | 29.41" | +0.20% | +40 mm | 60.1 mph | calculate → |
| 335/30R21 | 28.91" | -1.48% | +70 mm | 59.1 mph | calculate → |
| 345/30R21 | 29.15" | -0.67% | +80 mm | 59.6 mph | calculate → |
| 225/45R21 | 28.97" | -1.27% | -40 mm | 59.2 mph | calculate → |
| 305/40R21 | 30.61" | +4.29% | +40 mm | 62.6 mph | calculate → |
Plus / minus sizing: 20" and 22" rims
Same overall height on a different rim. Check wheel width and clearance before switching.
| Size | Diameter | Difference | Width | Speedo at 60 | |
|---|---|---|---|---|---|
| 265/45R20 common | 29.39" | +0.15% | 0 mm | 60.1 mph | compare → |
| 265/35R22 | 29.30" | -0.15% | 0 mm | 59.9 mph | compare → |
| 295/40R20 | 29.29" | -0.19% | +30 mm | 59.9 mph | compare → |
| 235/50R20 | 29.25" | -0.32% | -30 mm | 59.8 mph | compare → |
| 275/35R22 | 29.58" | +0.79% | +10 mm | 60.5 mph | compare → |
| 305/40R20 | 29.61" | +0.89% | +40 mm | 60.5 mph | compare → |
| 315/30R22 | 29.44" | +0.32% | +50 mm | 60.2 mph | compare → |
| 305/30R22 | 29.20" | -0.48% | +40 mm | 59.7 mph | calculate → |
Try another size against 265/40R21
Questions
What size is 265/40R21 in inches?
265/40R21 is about 29.3" tall and 10.4" wide on a 21-inch rim — roughly a 29.5x10.50R21 in inch sizing.
What does 265/40R21 mean?
265 mm section width, sidewall 40% of the width (4.17"), radial construction, 21-inch rim.
What tire sizes are equivalent to 265/40R21?
On the same 21" rim, within 3% of the diameter: 235/45R21 (-0.07%), 305/35R21 (+0.20%), 345/30R21 (-0.67%), 295/35R21 (-0.74%), 255/40R21 (-1.07%), 275/40R21 (+1.07%).
How many revolutions per mile does a 265/40R21 tire make?
About 687 revolutions per mile (circumference 92.2").
How these numbers are computed
Diameter = rim + 2 × sidewall, sidewall = width × aspect ÷ 100, circumference = π × diameter, revolutions per mile = 63,360 ÷ circumference. Real tires differ by brand by a few tenths of an inch. Last reviewed October 14, 2026.