ElpiAuto33X12.50R20 in metric
A 33X12.50R20 is 33.0″ (838 mm) tall and 12.50″ (318 mm) wide on a 20″ wheel. Converted directly it reads 320/50R20; the nearest standard metric size is 325/50R20.
Your tire size
e.g. 235/75R15, 33X12.50R15, or 225/45R17 91V
Metric equivalents of 33X12.50R20
No standard metric size lands exactly on 33X12.50R20. The best compromise is 325/50R20 (−0.6% height, +8 mm width); the list is ranked by height and width together, all on a 20″ wheel within ±3%.
| Size | Diameter | Height vs 33X12.50R20 | Width vs 33X12.50R20 |
|---|---|---|---|
| 325/50R20 | 32.8″ · 833 mm | −0.6% | +8 mm |
| 305/55R20 | 33.2″ · 844 mm | +0.6% | −13 mm |
| 315/50R20 | 32.4″ · 823 mm | −1.8% | −3 mm |
| 315/55R20 | 33.6″ · 855 mm | +1.9% | −3 mm |
| 335/50R20 | 33.2″ · 843 mm | +0.6% | +18 mm |
33X12.50R20 dimensions
Computed from the size code; moulded tires vary by brand by roughly 1–3%.
| Dimension | Inches | Millimetres |
|---|---|---|
| Overall diameter | 33.0″ | 838 |
| Section width | 12.50″ | 318 |
| Sidewall height | 6.50″ | 165 |
| Circumference | 103.7″ | 2633 |
| Revolutions per mile | 611 | — |
| Revolutions per km | — | 380 |
The same height on other wheels
If you are changing wheel diameter but want to keep a 33.0″ overall height, these metric sizes come closest (within 2%).
| Wheel | Size | Diameter | Difference |
|---|---|---|---|
| 15″ | 305/75R15 | 33.0″ | +0.0% |
| 16″ | 335/65R16 | 33.1″ | +0.4% |
| 17″ | 315/65R17 | 33.1″ | +0.4% |
| 18″ | 345/55R18 | 32.9″ | −0.2% |
| 22″ | 295/50R22 | 33.6″ | +1.9% |
Wheel width and neighbouring sizes
A 318 mm-wide tire mounts on 9.5–12.0″ wide wheels (the usual approved range; the middle is ideal).
One step down is 275/55R20: −3.3% in diameter. With a speedometer calibrated for 33X12.50R20, an indicated 60 mph would be 58.0 mph on 275/55R20.
One step up is 305/55R20: +0.6% in diameter. With a speedometer calibrated for 33X12.50R20, an indicated 60 mph would be 60.4 mph on 305/55R20.
Figures are geometric: overall diameter = wheel + 2 × sidewall, 25.4 mm per inch. Check the tire maker's data sheet for the exact moulded size before buying.