A wheel's bolt pattern indicates how the holes in the wheel will fit the lugs. The first number in the pattern is the number of bolts. It's followed by an "x." The final number is the diameter of the circle formed by the bolts, written either in millimeters or inches. For example, a 5x4.5 bolt pattern means the wheel has five bolt holes spaced in a circle that measures 4.5 inches in diameter. If a wheel has an even number of bolts, you can easily measure the diameter from the center of one bolt to the center of the opposite bolt; a five-lug pattern, though, requires a specialized measurement.
Measure from the center of one bolt to the outside edge of another bolt that's two bolts away, using a tape measure marked in inches. (The outside edge is the side of the bolt that's farthest from the center of the wheel.)
Convert fractional inches to decimals. Every 1/8 is equal to .125, so for example, 5 3/8 inches would be 5 plus 3 times .125, or 5.375.
Round the measurement to the nearest bolt pattern that's available. Express the final result as "5x" followed by the measurement. To convert the measurement to millimeters, multiply the result by 25.4, and round it to the nearest bolt pattern available. For example, you might round a result in inches to 5x4.5, a common bolt pattern, if the measurement is within a few hundredths of an inch of 4.5 inches. You might round a metric measurement to either 5x100 or 5x114.3 if the result is within a few millimeters of either 100 or 114.3. Check with the company where you're buying new wheels to see what the common sizes are.
