Sorry Babe Longsleeve

Place the end of a measuring tape beside the collar at the top of the shirt (high point shoulder). Pull the tape to the bottom of the shirt.

Lay the garment down on a flat surface and measure it from left to right across the chest, about 2cm below the arms.

Lay the garment down on a flat surface and pull the sleeve away from the shirt. Measure the sleeve from the tip of the shoulder to the opening of the sleeve.
Measurements are provided by suppliers and garments may run smaller or larger with a difference of +/-2.5cm (1 in)