Calculate speed in miles per hour or feet per second using our speed calculator or keep reading to learn more about each unit of measure. Since one mile per hour is equal to 1.466667 feet per second, you can use this simple formula to convert: feet per second = miles per hour × 1.466667 The speed in feet per second is equal to the speed in miles per hour multiplied by 1.466667. For example, here's how to convert 5 miles per hour to feet per second using the formula above.