Start with a well-fitting dress shirt laid flat and buttoned
Place the shirt on a smooth surface with the sleeves fully extended
Measure from the center back of the neck, where the collar meets the yoke
Run the tape measure over the shoulder seam and down to the end of the cuff
Keep the tape straight and follow the natural curve of the sleeve
Record the measurement in inches or centimeters
For a body measurement, bend your elbow slightly and measure from the center back of the neck to the wrist bone
Add or compare this measurement to the shirt size chart
Repeat on both sleeves if you want to check for symmetry