MM → Inches
109 mm to inches
109 millimeters equals 4.291339 inches — or about 4 5/16" (nearest 1/16″).
Decimal
4.2913 in
Fraction
4 5/16"
Centimeters
10.9 cm
Feet
0.3576 ft
mm
4.291339
in≈ 4 5/16" (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 = 109 ÷ 25.4 = 4.291339
Why 109 mm = 4.2913 in
Since 1 inch is defined as exactly 25.4 millimeters, 109 mm converts to 4.291339 inches. Rounded to the nearest 1/16″ that's 4 5/16", which is what you'd read off a standard imperial ruler.