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Woodworking Math

9/64 inch in decimal and mm

Decimal inches

0.140625 in

0.1406 in to four places

Millimetres

3.571875 mm

From the standard, the international inch, 25.4 mm exactly

The math

  1. A fraction is its top number divided by its bottom number: 9/64 in = 9 ÷ 64 = 0.140625 in.
  2. An inch is exactly 25.4 mm, so 0.140625 × 25.4 = 3.571875 mm, or 3.572 mm to three places.
  3. In feet, divide by 12: 0.140625 ÷ 12 = 0.011719 ft. In centimetres, divide the mm by 10: 0.3571875 cm.

9/64 to the nearest 1/8, 1/16, 1/32

A tape or rule marked more coarsely than 64ths can’t show 9/64 exactly. The nearest marks, and how far off each is (plus means the mark is bigger; a size exactly halfway goes to the bigger mark):

NearestMarkOff by (in)Off by (mm)
1/81/8 in−0.015625−0.397
1/161/8 in−0.015625−0.397
1/325/32 in+0.015625+0.397

Drills, plywood and lumber at 9/64 in

Drills either side of 9/64 in
DrillSizeOff by
3.5 mm0.1378 in−0.0719 mm
3.6 mm0.1417 in+0.0281 mm

Every drill is on the drill bit size chart.

Bits of this size

Sizes either side

FractionDecimalmm
1/8 in0.125 in3.175 mm
5/32 in0.15625 in3.969 mm

Every size is on the fraction to decimal chart; any other size goes in the fraction to decimal calculator.