275/40R21 tire size
275/40R21 is a metric size: 29.7" tall, 10.8" wide, on a 21" rim — about a 29.5x11.00R21. The sidewall is 4.3" and the tire turns 680 times per mile.
275/40R21 specs
| Overall diameter (height) | 29.66" · 753 mm |
|---|---|
| Section width | 10.83" · 275 mm |
| Sidewall height | 4.33" · 110 mm (40% of width) |
| Rim diameter | 21" |
| Circumference | 93.18" · 2.367 m |
| Revolutions per mile | 680 (422 per km) |
| Inch (flotation) equivalent | 29.5x11.00R21 |
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 | |
|---|---|---|---|---|---|
| 265/40R21 common | 29.35" | -1.06% | -10 mm | 59.4 mph | compare → |
| 275/35R21 common | 28.58" | -3.65% | 0 mm | 57.8 mph | compare → |
| 295/35R21 | 29.13" | -1.79% | +20 mm | 58.9 mph | compare → |
| 275/45R21 | 30.74" | +3.65% | 0 mm | 62.2 mph | compare → |
| 255/40R21 | 29.03" | -2.12% | -20 mm | 58.7 mph | compare → |
| 265/35R21 | 28.30" | -4.58% | -10 mm | 57.3 mph | compare → |
| 295/40R21 | 30.29" | +2.12% | +20 mm | 61.3 mph | compare → |
| 285/45R21 | 31.10" | +4.84% | +10 mm | 62.9 mph | compare → |
| 285/40R21 | 29.98" | +1.06% | +10 mm | 60.6 mph | compare → |
| 265/45R21 | 30.39" | +2.46% | -10 mm | 61.5 mph | compare → |
| 325/30R21 | 28.68" | -3.32% | +50 mm | 58.0 mph | compare → |
| 285/35R21 | 28.85" | -2.72% | +10 mm | 58.4 mph | compare → |
| 315/30R21 | 28.44" | -4.11% | +40 mm | 57.5 mph | compare → |
| 315/35R21 | 29.68" | +0.07% | +40 mm | 60.0 mph | compare → |
| 245/40R21 | 28.72" | -3.19% | -30 mm | 58.1 mph | compare → |
| 305/30R21 | 28.20" | -4.91% | +30 mm | 57.1 mph | compare → |
| 315/40R21 | 30.92" | +4.25% | +40 mm | 62.5 mph | compare → |
| 255/45R21 | 30.04" | +1.26% | -20 mm | 60.8 mph | compare → |
| 245/45R21 | 29.68" | +0.07% | -30 mm | 60.0 mph | compare → |
| 255/50R21 | 31.04" | +4.65% | -20 mm | 62.8 mph | compare → |
| 235/50R21 | 30.25" | +1.99% | -40 mm | 61.2 mph | calculate → |
| 235/45R21 | 29.33" | -1.13% | -40 mm | 59.3 mph | calculate → |
| 305/35R21 | 29.41" | -0.86% | +30 mm | 59.5 mph | calculate → |
| 335/30R21 | 28.91" | -2.52% | +60 mm | 58.5 mph | calculate → |
| 345/30R21 | 29.15" | -1.73% | +70 mm | 59.0 mph | calculate → |
| 225/45R21 | 28.97" | -2.32% | -50 mm | 58.6 mph | calculate → |
| 305/40R21 | 30.61" | +3.19% | +30 mm | 61.9 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 | |
|---|---|---|---|---|---|
| 245/50R20 common | 29.65" | -0.05% | -30 mm | 60.0 mph | compare → |
| 275/45R20 common | 29.74" | +0.28% | 0 mm | 60.2 mph | compare → |
| 265/45R20 common | 29.39" | -0.92% | -10 mm | 59.5 mph | compare → |
| 285/35R22 | 29.85" | +0.65% | +10 mm | 60.4 mph | compare → |
| 275/35R22 | 29.58" | -0.28% | 0 mm | 59.8 mph | compare → |
| 305/40R20 | 29.61" | -0.19% | +30 mm | 59.9 mph | compare → |
| 315/30R22 | 29.44" | -0.74% | +40 mm | 59.6 mph | compare → |
| 325/30R22 | 29.68" | +0.05% | +50 mm | 60.0 mph | calculate → |
| 175/70R20 | 29.65" | -0.05% | -100 mm | 60.0 mph | calculate → |
Try another size against 275/40R21
Questions
What size is 275/40R21 in inches?
275/40R21 is about 29.7" tall and 10.8" wide on a 21-inch rim — roughly a 29.5x11.00R21 in inch sizing.
What does 275/40R21 mean?
275 mm section width, sidewall 40% of the width (4.33"), radial construction, 21-inch rim.
What tire sizes are equivalent to 275/40R21?
On the same 21" rim, within 3% of the diameter: 245/45R21 (+0.07%), 315/35R21 (+0.07%), 305/35R21 (-0.86%), 265/40R21 (-1.06%), 285/40R21 (+1.06%), 235/45R21 (-1.13%).
How many revolutions per mile does a 275/40R21 tire make?
About 680 revolutions per mile (circumference 93.2").
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.