305/40R23 tire size
305/40R23 is a metric size: 32.6" tall, 12.0" wide, on a 23" rim — about a 32.5x12.00R23. The sidewall is 4.8" and the tire turns 619 times per mile.
305/40R23 specs
| Overall diameter (height) | 32.61" · 828 mm |
|---|---|
| Section width | 12.01" · 305 mm |
| Sidewall height | 4.80" · 122 mm (40% of width) |
| Rim diameter | 23" |
| Circumference | 102.44" · 2.602 m |
| Revolutions per mile | 619 (384 per km) |
| Inch (flotation) equivalent | 32.5x12.00R23 |
Equivalent sizes on a 23" 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 | |
|---|---|---|---|---|---|
| 285/40R23 | 31.98" | -1.93% | -20 mm | 58.8 mph | calculate → |
| 325/35R23 | 31.96" | -1.99% | +20 mm | 58.8 mph | calculate → |
| 275/40R23 | 31.66" | -2.90% | -30 mm | 58.3 mph | calculate → |
Try another size against 305/40R23
Questions
What size is 305/40R23 in inches?
305/40R23 is about 32.6" tall and 12.0" wide on a 23-inch rim — roughly a 32.5x12.00R23 in inch sizing.
What does 305/40R23 mean?
305 mm section width, sidewall 40% of the width (4.80"), radial construction, 23-inch rim.
What tire sizes are equivalent to 305/40R23?
On the same 23" rim, within 3% of the diameter: 285/40R23 (-1.93%), 325/35R23 (-1.99%), 275/40R23 (-2.90%).
How many revolutions per mile does a 305/40R23 tire make?
About 619 revolutions per mile (circumference 102.4").
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.