Keeping your grill covered when not in use keeps it clean and helps prevent corrosion. Measuring the overall dimensions of the grill will enable you to buy the correct size, since there are dozens of cover shapes and sizes. It's also a good idea to sketch the basic design of your grill, since covers also come in many shapes.
Sketch a simple picture of the shape of your charcoal or gas grill. Although you will measure the dimensions later, taking a basic picture of the grill to the store will help you find not only the right size but the right shape as well.
Measure the grill height from the top to the ground in inches, including the chimney height if you have a smoker-type grill.
Hold the tape measure to one side from the back of the grill to the front handle and write down the width.
Measure the grill length from the edge of one side to the other side, including shelves and side burners.
Shop for covers that are the same size or are an inch or two larger than the dimensions of your charcoal or gas grill.
Check the package illustration to be sure the cover is the same shape as your grill. If you have a shelf or side burners on both sides of the grill, then the cover will need to be in that same trapezoid shape.