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Woodworking Math

63/64 inch in decimal and mm

Decimal inches

0.984375 in

0.9844 in to four places

Millimetres

25.003125 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: 63/64 in = 63 ÷ 64 = 0.984375 in.
  2. An inch is exactly 25.4 mm, so 0.984375 × 25.4 = 25.003125 mm, or 25.003 mm to three places.
  3. In feet, divide by 12: 0.984375 ÷ 12 = 0.082031 ft. In centimetres, divide the mm by 10: 2.5003125 cm.

63/64 to the nearest 1/8, 1/16, 1/32

A tape or rule marked more coarsely than 64ths can’t show 63/64 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 in+0.015625+0.397
1/161 in+0.015625+0.397
1/321 in+0.015625+0.397

Drills, plywood and lumber at 63/64 in

Drills either side of 63/64 in
DrillSizeOff by
25 mm0.9843 in−0.0031 mm

Every drill is on the drill bit size chart.

Bits of this size

Sizes either side

FractionDecimalmm
31/32 in0.96875 in24.606 mm
1 in1 in25.400 mm

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