Use a measuring tape to determine the diameter of the neck, using the unbuttoned collar as a guide for where to place the measuring tape and record the measurement. Two fingers should fit comfortably between the shirt collar and neck to ensure a proper fit that isn't too snug.
- Lay a collared shirt out flat
- Measure the collar
- Record the measurement
Unbutton a collared shirt that fits well and lay it out flat.
Use a measuring tape to measure from the button hole on the collar to the stitching on the back of the collar's button.
Record the measurement, making sure to round to the nearest quarter inch.