Take your favorite shirt. Lay it flat and Measure it this way. Tape Measurer? You got one somewhere? This is the updated for "One World Water Symphony Orchestra" LONG SLEEVE SHIRT please be advised We Utilized a new technology which is referred to as sizes on our labels? But this will let you know what size you need before you buy *SIZES* SMALL Chest Width-18 inches-Length-27 inches. MEDIUM Width-20 inches-Length-28.75 Inches LARGE Width-21.75 inches-Length 29.75 inches XL (Also known as X-Large) Width-23.75 inches-Length-31.75 inches 2 XL (Also known as Double XL? YESSIR?) Width-25.75 inches-Length-32.75 inches /