To take car width measurements, use a 4-foot level to ensure that the vehicle is level, and measure the distance between the required measuring points across the car's bottom or top. Have someone assist you in this task, advises eHow.
Begin measuring a car's width by parking the automobile on a surface that is level and smooth. Station yourself on one side of the car, and ask your assistant to stand on the other side.
Choose the measuring points, which could be mirrors, tires or door handles, between which the width is to be determined. Measure between mirrors and doors if the car width measurement is required for parking the vehicle in a narrow space. Measure car width between wheels if hitching a trailer to it.
Place the level on one measuring point of the vehicle, and ask your assistant to do the same. Ensure that the bubble of the level lies at its center and between its two lines. This ensures that the vehicle is vertically level.
Hold one end of the measuring tape, and pass it over the car's top or under its bottom to the assistant. Ask the assistant to place the measuring tape at the level's end, and give the tape a tug to ensure that it is held across the car tautly.
Pull the measuring tape until it reaches the level's end on your side, and note the measurement at this point. This measurement is the car's width.