245/70R16 tyre size
749.4 mm diameter
29.50 in · 171.5 mm sidewall · 2.35 m rolling circumference · 425 rev/km
Reading 245/70R16
| 245 | Tread width in millimetres |
| 70 | Aspect ratio — sidewall height as a percentage of the width, so 245 × 70% = 171.5 mm |
| R | Radial construction, which is almost every road tyre made since the 1970s |
| 16 | Rim diameter in inches — 406.4 mm |
The aspect ratio is the part that catches people: it is a percentage of the width, not a fixed height. Widen the tread and keep the same aspect number and the tyre also gets taller. That is why 245/70R16 and a size with a smaller aspect number on a larger rim can be the same overall diameter.
The numbers
| Tread width | 245 mm · 9.65 in |
| Sidewall height | 171.5 mm · 6.75 in |
| Rim diameter | 16 in · 406.4 mm |
| Overall diameter | 749.4 mm · 29.50 in |
| Rolling circumference | 2354.3 mm · 2.35 m |
| Revolutions per kilometre | 425 |
| Revolutions per mile | 684 |
Sizes that fit in place of 245/70R16
A replacement is judged on rolling diameter, because that is what the speedometer, the ABS and the gearing all depend on. Anything within about 1% is treated as interchangeable; beyond 3% the speedometer error stops being ignorable.
| Size | Diameter | Difference | Speedometer at an indicated 100 |
|---|---|---|---|
| 275/45R20 | 755.5 mm | +0.81% | 100.8 km/h actual |
| 295/35R21 | 739.9 mm | -1.27% | 98.7 km/h actual |
| 235/60R18 | 739.2 mm | -1.36% | 98.6 km/h actual |
| 255/55R18 | 737.7 mm | -1.56% | 98.4 km/h actual |
| 235/65R17 | 737.3 mm | -1.61% | 98.4 km/h actual |
| 315/35R20 | 728.5 mm | -2.79% | 97.2 km/h actual |
| 275/40R20 | 728.0 mm | -2.86% | 97.1 km/h actual |
Diameter is only half the question — the replacement also has to suit the rim width and the vehicle's load and speed ratings. Check the placard in the door frame before buying.
Other 16-inch sizes
| Size | Sidewall | Diameter |
|---|---|---|
| 195/55R16 | 107.3 mm | 620.9 mm |
| 205/55R16 | 112.8 mm | 631.9 mm |
| 205/60R16 | 123.0 mm | 652.4 mm |
| 205/65R16 | 133.3 mm | 672.9 mm |
| 215/55R16 | 118.3 mm | 642.9 mm |
| 215/60R16 | 129.0 mm | 664.4 mm |
| 215/65R16 | 139.8 mm | 685.9 mm |
| 265/70R16 | 185.5 mm | 777.4 mm |
Frequently asked questions
What does 245/70R16 mean?
245 is the tread width in millimetres, 70 is the sidewall height as a percentage of that width — so 245 × 70% = 171.5 mm of sidewall — and R16 is a radial tyre on a 16-inch rim. Overall diameter is 16 × 25.4 + 2 × 171.5 = 749.4 mm.
What is the overall diameter of a 245/70R16?
749.4 mm (29.50 inches), with a rolling circumference of 2.35 m — about 425 revolutions per kilometre.
What size is equivalent to a 245/70R16?
275/45R20 (+0.81%) — all within 1% of this diameter, which is the band inside which a manufacturer will list alternatives for the same car. Width and rim differ; rolling diameter does not.
How much does changing tyre size affect the speedometer?
A speedometer counts wheel revolutions, so it reads in proportion to the rolling diameter it was calibrated for. Fitting a tyre 1% larger makes the speedometer read 1% low — at an indicated 100 km/h you are doing 101. Most jurisdictions expect a speedometer to never under-read, which is why replacements are kept within about 3% and why the factory tyre usually reads a little high to begin with.