Inflate the cuff. Rapidly pump the bulb to inflate the cuff. Keep pumping until the needle on the gauge reaches 180mmHg. The pressure from the cuff will occlude a large artery in the bicep, temporarily cutting off blood flow. This is why the pressure from the cuff can feel a little uncomfortable or strange.
Release the valve. Gently turn the valve on the bulb counter-clockwise, so that the air in the cuff is released steadily, but at a slow pace. Keep an eye on the gauge; for best accuracy, the needle should be moving downwards at a rate of 3mm per second.
Releasing the valve while you hold the stethoscope can be a little tricky. Try releasing the valve with the hand on your cuff arm, while holding the stethoscope with your free arm.
If there is someone nearby, ask him to assist you. An additional pair of hands can make the process much easier.
Note your systolic blood pressure. As the pressure drops, use the stethoscope to listen for a thumping or knocking sound. When you hear the first thump, make a note of the pressure on the gauge. This is your systolic blood pressure.
The systolic number represents the pressure your blood flow exerts on the walls of an artery after the heart beats or contracts. It is the higher number of the two blood pressure readings, and when blood pressure is written down, it appears at the top.
The clinical name for the thumping sounds your hear is "Korotkoff sounds."
Note your diastolic blood pressure. Keep watching the gauge, while using the stethoscope to listen to the thumping noises. Eventually the hard thumping noises will turn into a "whooshing" sound. It is helpful to note this change, as it indicates that you are close to your diastolic blood pressure. As soon as the whooshing noise subsides, and you hear only silence, make a note of the pressure on the gauge. This is your diastolic blood pressure.
The diastolic number represents the pressure your blood flow exerts on the walls of an artery when your heart relaxes between contractions. It is the lower number of the two blood pressure readings, and when blood pressure is written down, it appears at the bottom.
Don't worry if you miss a reading. If you miss the exact measure of either number, it's perfectly acceptable to pump the cuff back up a little to catch it.
Just don't do it too much (more than twice) as this can affect accuracy.
Alternatively, you can switch the cuff to the other arm and repeat the process again.
Check your blood pressure again. Blood pressure fluctuates within minutes (sometimes dramatically) so if you take two readings within about a ten-minute period, you can come up with a more accurate average number.
For the most accurate results, check your blood pressure a second time, five to ten minutes after the first go.
It may also be a good idea to use your other arm for the second reading, especially if your first reading was abnormal.