How do I check the accuracy of a speedometer?

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FAQ Category

Equipment

FAQ Answer

A vehicle's speed and accuracy of the speedometer can be made by measuring the time it takes to travel one mile. An option is to download an app from a reputable source from Google Play or the Apple Play or off Google Play store to test your speedometer. Alternatively, you can conduct the test by setting the cruise at one speed and measure the time it takes to travel between two green mile markers on Interstate or other US/state highway.

Using the seconds on the left on the chart below, the corresponding mph is listed in the right column.

Seconds	Miles Per Hour
45.5	79
46	78
46.7	77
47	76
48	75
48.5	74
49	73
50	72
50.5	71
51.5	70
52	69
53	68
53.5	67
54.4	66
55	65
56	64
57	63
58	62
59	61
60	60
61	59
62	58
63	57
64	56
65.5	55
66.5	54
68	63
69	52

(Revised 07-2003)