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Woodworking Math

5/64 inch in decimal and mm

Decimal inches

0.078125 in

0.0781 in to four places

Millimetres

1.984375 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: 5/64 in = 5 ÷ 64 = 0.078125 in.
  2. An inch is exactly 25.4 mm, so 0.078125 × 25.4 = 1.984375 mm, or 1.984 mm to three places.
  3. In feet, divide by 12: 0.078125 ÷ 12 = 0.00651 ft. In centimetres, divide the mm by 10: 0.1984375 cm.

5/64 to the nearest 1/8, 1/16, 1/32

A tape or rule marked more coarsely than 64ths can’t show 5/64 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+0.046875+1.191
1/161/16 in−0.015625−0.397
1/323/32 in+0.015625+0.397

Drills, plywood and lumber at 5/64 in

Drills either side of 5/64 in
DrillSizeOff by
1.9 mm0.0748 in−0.0844 mm
2 mm0.0787 in+0.0156 mm

Every drill is on the drill bit size chart.

Bits of this size

Sizes either side

FractionDecimalmm
1/16 in0.0625 in1.588 mm
3/32 in0.09375 in2.381 mm

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