Choosing the right violin size for the student is essential for a correct start. It should be based on the player's physique, arm length, height, and age range.

Measuring the player's left arm length is used to compare and choose the correct violin size. Measure from the player's neck (base of the neck) to the center of the palm, then compare the left arm length with the violin size comparison table.

Choosing the correct violin size by measuring the violin: using the player's left hand, if the player can curl their fingers around the scroll (head) of the violin past the halfway point, it means the player can use that violin.

If the player cannot curl their fingers around the scroll of the violin, it means the violin is too large, unsuitable for their physique, causes difficulty in playing, and may make the player discouraged and eventually quit.

Choosing the correct bow size: use the bow to measure from the player's right shoulder to the tip of the middle finger. If the player's middle finger can extend to the tip of the frog (end of the horsehair), it means the player can use that bow size. This can also be used as a criterion for choosing violin size. For example, if the middle finger tip reaches the frog of a 4/4 bow, the player can use a 4/4 violin as well.

How to measure: Have the player sit on a chair with both knees bent at 90 degrees. Adjust the cello endpin height so the left leg touches the top of the lower bout. See the image.

If the cello is the right size for the player, the breastbone should rest against the top of the upper bout, and the C-string peg should be near the player's left ear. From this position, the player can reach the end of the fingerboard. See the image.

Choosing the right double bass size for the student. The standard size for adults is 3/4. Larger double basses that are very rare and not commonly used are 7/8 and 4/4.