If you have multiple sized instruments available to try, you can determine the correct size for a student by having them hold the instrument. Have the student rest the instrument on their left shoulder, place their chin on the chinrest, and reach their left arm out towards the other end of the instrument.

With the correct size, the student should be able to wrap their fingers around the scroll of the instrument with a slight bend in their elbow.

If you do not have instruments to try, you can estimate an appropriate size by measuring the arm length of the student.

Have the student extend their left arm fully straight to the side, parallel to the floor. Measure from the base of the neck (where it meets the shoulder) to the middle of the palm.

Cellos - With multiple sizes available, have the student sit in a chair with good posture. Knees should be bent at a right angle and the feet should be flat on the floor. A correctly-sized instrument should contact the lower bout with the left knee, upper edge against the student's chest, and the C peg should line up with the ear.

Basses - The height of the student is the main factor in determining an appropriate sized bass. On a comfortable instrument, the nut at the top of the bridge should align with the forehead when both the student and instrument are standing tall. In playing position, the student should be able to reach around the instrument and touch the bridge while still standing flat on the ground.

If you do not have instruments to try, you can estimate an appropriate size by measuring the height of the student. Even though a younger student may be tall enough for a larger size, they may be sized with a smaller instrument to start.