The measures are human-scale and, once learned, easy to use. A pint of beer is easier to order than 500ml, and a half-pound is easier to think of than 250g. Many English system measures work well with fractions, which are convenient in everyday life.

Without the metric system, we’d have a different International System of Units, the metric system is important because 1mm is 0.1cm, 1 cm is 0.01m, with the imperial system the conversion is tedious. The metric system has been adopted by almost every country in the world.

Conversion Ratio (or Unit Factor): While the Metric System simply moves the decimal point to convert between its measurements’ prefixes, the English System requires a conversion ratio (or unit factor) to move between measurements. In the Metric System, the prefix itself gives the needed conversion ratio.

The two systems are used interchangeably in the scientific and technical communities. B. The English system is more commonly used in Europe than in the United States. The SI system, which is based on the metric system, has been more widely adopted than the English system, which is harder to use.

For both metric and standard bolts, the head size is the distance across the flats. For standard bolts, the head size is measured in inches or fractions of an inch. For metric bolts, head size is measured in millimeters. However, metric bolt head size is measured in millimeters.

While many of the sizes won’t be used on your Benz, if you happen to have a GM vehicle around, you’re gonna need both SAE and all those in-between Metric sizes.

As with all wrenches, you have the choice between U.S., also known as standard, or metric sizes. American cars are assembled with nuts and bolts that use standard measurements while foreign cars almost exclusively use metric measurements.

Common thread diameters used for lug nuts in SAE sizes are 7/16, 1/2, 9/16 and 5/8”. Common metric thread diameters are 12 mm and 14 mm.