MM → Inches
42 mm to inches
42 millimeters equals 1.653543 inches — or about 1 5/8" (nearest 1/16″).
Decimal
1.6535 in
Fraction
1 5/8"
Centimeters
4.2 cm
Feet
0.1378 ft
mm
1.653543
in≈ 1 5/8" (nearest 1/16)
1 in = 25.4 mm · tolerance ±0.0001
Formula
To convert mm to inches, divide by 25.4:
inches = mm ÷ 25.4
inches = 42 ÷ 25.4 = 1.653543
Why 42 mm = 1.6535 in
Since 1 inch is defined as exactly 25.4 millimeters, 42 mm converts to 1.653543 inches. Rounded to the nearest 1/16″ that's 1 5/8", which is what you'd read off a standard imperial ruler.