Tire to RPM Ratio Chart

The following chart shows engine rpm at 60 mph for various combinations of final drive ratio and tire diameter. If you want to determine rpm at a speed other than 60, or for a combination of ratio and tire size not indicated here, the formula is:

MPH x Drive Ratio x 336 = RPM
Tire Diameter

If you’d like to know your speed at a given rpm, the formula is:

RPM x Tire Diameter x 336 = MPH
Drive Ratio x 336

In both cases, “336” is simply a constant to convert the tire diameter to the linear distance the tire travels.

To determine your vehicle’s engine rpm with its present tires, simply measure the diameter with a tape. If the tires have a convex tread surface, be sure to allow for it when you measure them.

Better Gas Mileage Near Factory Ratio More Power
Engine RPM at 65 mph

Gear Ratio

3.31 3.42 3.55 3.73 3.91 4.11 4.27 4.56 4.88 5.13 5.29 5.38
27″ 2677 2766 2872 3017 3163 3325 3454 3689 3947 4150 4279 4352
28″ 2582 2668 2769 2909 3050 3206 3331 3557 3806 4001 4126 4196
29″ 2493 2576 2674 2809 2945 3095 3216 3434 3675 3863 3984 4052
30″ 2410 2490 2584 2715 2846 2992 3109 3320 3553 3735 3851 3917
31″ 2332 2409 2501 2628 2755 2896 3008 3213 3838 3614 3727 3790
32″ 2259 2334 2423 2546 2696 2805 2914 3112 3331 3501 3610 3672
33″ 2191 2263 2349 2469 2588 2720 2826 3018 3230 3395 3501 3561
34″ 2126 2197 2280 2396 2512 2640 2743 2929 3135 3295 3398 3456
35″ 2065 2134 2215 2328 2440 2565 2664 2845 3045 3201 3301 3357
36″ 2008 2075 2154 2263 2372 2493 2590 2766 2961 3112 3209 3264
37″ 1954 2019 2095 2203 2308 2426 2520 2692 2881 3028 3123 3176
38″ 1902 1966 2040 2144 2247 2362 2454 2621 2805 2948 3040 3092
39″ 1854 1915 1988 2089 2190 2302 2391 2554 2733 2873 2962 3013
40″ 1807 1867 1938 2037 2135 2244 2331 2490 2664 2801 2888 2937
41″ 1763 1822 1891 1987 2083 2189 2275 2429 2599 2733 2818 2866
42″ 1721 1778 1846 1940 2033 2137 2220 2371 2538 2668 2751 2798
43″ 1681 1737 1803 1894 1986 2087 2169 2316 2479 2606 2687 2733
44″ 1643 1698 1762 1851 1941 2040 2119 2263 2422 2546 2626 2670