How to Convert 3mm to Inches
3 mm ÷ 25.4 = 0.1181 inches. To find the nearest 32nd, multiply by 32: 0.1181 × 32 = 3.78, which rounds to 4/32.
On a Tape Measure
Standard US tape measures show marks at every 1/16 inch. The nearest mark to 3mm is the 1/8″ mark. For rough layout work, use the 1/8″ mark.