255/40R13 tire size
255/40R13 is a metric size: 21.0" tall, 10.0" wide, on a 13" rim — about a 21x10.00R13. The sidewall is 4.0" and the tire turns 959 times per mile.
255/40R13 specs
| Overall diameter (height) | 21.03" · 534 mm |
|---|---|
| Section width | 10.04" · 255 mm |
| Sidewall height | 4.02" · 102 mm (40% of width) |
| Rim diameter | 13" |
| Circumference | 66.07" · 1.678 m |
| Revolutions per mile | 959 (596 per km) |
| Inch (flotation) equivalent | 21x10.00R13 |
Equivalent sizes on a 13" 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 | |
|---|---|---|---|---|---|
| 225/45R13 | 20.97" | -0.28% | -30 mm | 59.8 mph | calculate → |
| 165/65R13 | 21.44" | +1.97% | -90 mm | 61.2 mph | calculate → |
| 215/50R13 | 21.46" | +2.06% | -40 mm | 61.2 mph | calculate → |
| 155/70R13 | 21.54" | +2.43% | -100 mm | 61.5 mph | calculate → |
Try another size against 255/40R13
Questions
What size is 255/40R13 in inches?
255/40R13 is about 21.0" tall and 10.0" wide on a 13-inch rim — roughly a 21x10.00R13 in inch sizing.
What does 255/40R13 mean?
255 mm section width, sidewall 40% of the width (4.02"), radial construction, 13-inch rim.
What tire sizes are equivalent to 255/40R13?
On the same 13" rim, within 3% of the diameter: 225/45R13 (-0.28%), 165/65R13 (+1.97%), 215/50R13 (+2.06%), 155/70R13 (+2.43%).
How many revolutions per mile does a 255/40R13 tire make?
About 959 revolutions per mile (circumference 66.1").
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.