MEASUREMENT SYSTEM

Two systems of weights and measures exist side by side in the United States—the Imperial or U.S. customary system and the international or metric system. The basic unit of linear measurement in the Imperial system is the inch. The basic unit of linear measurement in the metric system is the meter. The meter is easily broken down into smaller units, such as the centimeter (1⁄100 meter) and millimeter (1⁄1,000 meter).

All units of measurement in the metric system are related to each other by a factor of 10. Every metric unit can be multiplied or divided by the factor of 10 to get larger units (multiples) or smaller units (submultiples). This makes the metric system much easier to use, with less chance of math errors than when using the Imperial system (Figure).

The United States passed the Metric Conversion Act in 1975 in an attempt to get American industry and the general public to use the metric system, as the rest of the world does. While the general public has been slow to drop the customary measuring system of inches, gallons, and pounds, many industries, led by the automotive industry, have now adopted the metric system for the most part.

Nearly all vehicles are now built to metric standards. Technicians must be able to measure and work with both systems of measurement. The following are some common equivalents in the two systems:

Linear Measurements

1 meter (m) 39.37 inches (in.)

1 centimeter (cm) 0.3937 inch

1 millimeter (mm) 0.03937 inch

1 inch 2.54 centimeters

1 inch 25.4 millimeters

1 mile 1.6093 kilometers

Square Measurements

1 square inch 6.452 square centimeters

1 square centimeter 0.155 square inch

Volume Measurements

1 cubic inch 16.387 cubic centimeters

1,000 cubic centimeters 1 liter (l)

1 liter (l) 61.02 cubic inches

1 gallon 3.7854 liters

Weight Measurements

1 ounce 28.3495 grams

1 pound 453.59 grams

1,000 grams 1 kilogram

1 kilogram 2.2046 pounds

Temperature Measurements

1°Fahrenheit (F) 9⁄5C 32°

1°Celsius (C) 5⁄9(F – 32°)

Pressure Measurements

1 pound per square inch (psi) 0.07031 kilogram(kg) per square centimeter

1 kilogram per square centimeter 14.22334 pounds per square inch

1 bar 14.504 pounds per square inch

1 pound per square inch 0.06895 bar

1 atmosphere 14.7 pounds per square inch

Torque Measurements

10 foot-pounds (ft.-lb) 13.558 Newton meters (N-m)

1 N-m 0.7375 ft.-lb

1 ft.-lb 0.138 m kg

1 cm kg 7.233 ft.-lb

10 cm kg 0.98 N-m