MM → Inches

31 mm to inches

31 millimeters equals 1.220472 inches — or about 1 1/4" (nearest 1/16″).

Decimal

1.2205 in

Fraction

1 1/4"

Centimeters

3.1 cm

Feet

0.1017 ft

Millimeters (mm)

Inches (in)

1.220472

≈ 1 1/4" (nearest 1/16)

1 in = 25.4 mm · tolerance ±0.0001

Nearby values

30.5 mm 31.75 mm 31.8 mm 30 mm 32 mm 29 mm 33 mm 28.6 mm 28.5 mm 28 mm

Precision

1.2205

Inches

31.0 mm · max 100

Ref · 25.4 mm/in

Drag to set

Formula

To convert mm to inches, divide by 25.4:

inches = mm ÷ 25.4
inches = 31 ÷ 25.4 = 1.220472

Why 31 mm = 1.2205 in

Since 1 inch is defined as exactly 25.4 millimeters, 31 mm converts to 1.220472 inches. Rounded to the nearest 1/16″ that's 1 1/4", which is what you'd read off a standard imperial ruler.