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Woodworking Math

41/64 inch in decimal and mm

Decimal inches

0.640625 in

0.6406 in to four places

Millimetres

16.271875 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: 41/64 in = 41 ÷ 64 = 0.640625 in.
  2. An inch is exactly 25.4 mm, so 0.640625 × 25.4 = 16.271875 mm, or 16.272 mm to three places.
  3. In feet, divide by 12: 0.640625 ÷ 12 = 0.053385 ft. In centimetres, divide the mm by 10: 1.6271875 cm.

41/64 to the nearest 1/8, 1/16, 1/32

A tape or rule marked more coarsely than 64ths can’t show 41/64 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)
1/85/8 in−0.015625−0.397
1/165/8 in−0.015625−0.397
1/3221/32 in+0.015625+0.397

Drills, plywood and lumber at 41/64 in

Drills either side of 41/64 in
DrillSizeOff by
16 mm0.6299 in−0.2719 mm
16.5 mm0.6496 in+0.2281 mm

Every drill is on the drill bit size chart.

Bits of this size

Sizes either side

FractionDecimalmm
5/8 in0.625 in15.875 mm
21/32 in0.65625 in16.669 mm

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