To obtain accurate blood pressure readings it is important to use the correct size cuff. To measure the circumference of your arm use a cloth tape measure and place the tape midway between your elbow and shoulder and wrap the measure around the arm. Do not pull it too tight, just tight enough to prevent  the tape sliding up or down your arm. Take note of the measurement in centimetres.

Most well known brands of cuffs are sized using the centimetre scale. Check the advertisement to select the correct size cuff for your use.