1 1/4 inches to mm

Decimal: 1.25 inches

1 1/4 inches (1.25 inches) = 31.75 mm exactly (3.175 cm). The international inch is 25.4 mm, so multiply the inch value by 25.4.

Millimeters
31.75
Decimal inches
1.2500
Nearest 1/64
1 1/4 in (exact on 1/64)

The inches fraction result is rounded to the nearest 1/64 fraction.

1 1/4 inches to mm conversion

1 1/4 inches (1.25 inches) × 25.4 = 31.75 mm. Reverse: 31.75 ÷ 25.4 = 1.25 in.

1 1/4 inches to mm calculator

Use the converter at the top. Type a decimal or a fraction (1/16, 3 1/2). Millimeters update from the same engine as the inch to mm hub (1 in = 25.4 mm).

How to convert 1 1/4 inches to mm

  1. Write the length as a decimal inch if needed: 1 1/4 in = 1.25 in (1.25 inches).
  2. Multiply by 25.4: 1.25 × 25.4 = 31.75 mm.
  3. Optional centimeters: divide millimeters by 10 → 3.175 cm.

Nearest metric size

The nearest metric size is 32 mm, 0.25 mm larger than 31.75 mm.

32 mm is 0.25 mm larger than 1 1/4 inch (31.75 mm). 30 mm is 1.75 mm smaller. 1.25 inches is the decimal form of 1 1/4, not 1/4 inch (6.35 mm).

1 1/4 inches is 31.75 mm, not a whole millimeter. Whole-millimeter neighbors:

  • 31 mm is 0.75 mm smaller than 1 1/4 inches.
  • 32 mm is 0.25 mm larger than 1 1/4 inches.

Nearby inch fractions

Sixteenth-inch steps from the same 1 in = 25.4 mm factor. Linked rows have their own pages. The full fraction table is on inch to mm.

InchesDecimalMillimeters
1 in125.4 mm
1 1/16 in1.062526.9875 mm
1 1/8 in1.12528.575 mm
1 3/16 in1.187530.1625 mm
1 1/4 in1.2531.75 mm
1 5/16 in1.312533.3375 mm
1 3/8 in1.37534.925 mm
1 7/16 in1.437536.5125 mm
1 1/2 in1.538.1 mm

Other inch fractions to mm

FAQ

  • How many mm is 1 1/4 inches?

    1 1/4 inches is 31.75 mm exactly. 1.25 × 25.4 = 31.75. That is the decimal 1.25 inches, not 1/4 inch (6.35 mm).

  • What is 1.25 inches in mm?

    1.25 inches is 1 1/4 inches: 31.75 mm exactly (3.175 cm).

  • Is 32 mm the same as 1 1/4 inch?

    No. 1 1/4 inch is 31.75 mm. 32 mm is 0.25 mm larger. 30 mm is 1.75 mm smaller.