Inches to Millimeter nversion Example. Task: nvert 24 inches to millimeters (show work) Formula: in x 25.4 = mm Calculations: 24 in x 25.4 = 609.6 mm Result: 24 inches is equal to 609.6 mm..MM Imm 2mm m 4mm 5mm 6mm 7mm 8mm 9mm 10mm 1 Imm 12mm 1m 14mm 15mm 16mm 17mm 18mm 19mm 20mm 21mm 22mm 2m 24mm 25mm 26mm 27mm.