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Woodworking Math

13/64 inch in decimal and mm

Decimal inches

0.203125 in

0.2031 in to four places

Millimetres

5.159375 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: 13/64 in = 13 ÷ 64 = 0.203125 in.
  2. An inch is exactly 25.4 mm, so 0.203125 × 25.4 = 5.159375 mm, or 5.159 mm to three places.
  3. In feet, divide by 12: 0.203125 ÷ 12 = 0.016927 ft. In centimetres, divide the mm by 10: 0.5159375 cm.

13/64 to the nearest 1/8, 1/16, 1/32

A tape or rule marked more coarsely than 64ths can’t show 13/64 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)
1/81/4 in+0.046875+1.191
1/163/16 in−0.015625−0.397
1/327/32 in+0.015625+0.397

Drills, plywood and lumber at 13/64 in

Drills either side of 13/64 in
DrillSizeOff by
5.1 mm0.2008 in−0.0594 mm
5.2 mm0.2047 in+0.0406 mm

Every drill is on the drill bit size chart.

Bits of this size

Sizes either side

FractionDecimalmm
3/16 in0.1875 in4.763 mm
7/32 in0.21875 in5.556 mm

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