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Woodworking Math

45/64 inch in decimal and mm

Decimal inches

0.703125 in

0.7031 in to four places

Millimetres

17.859375 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: 45/64 in = 45 ÷ 64 = 0.703125 in.
  2. An inch is exactly 25.4 mm, so 0.703125 × 25.4 = 17.859375 mm, or 17.859 mm to three places.
  3. In feet, divide by 12: 0.703125 ÷ 12 = 0.058594 ft. In centimetres, divide the mm by 10: 1.7859375 cm.

45/64 to the nearest 1/8, 1/16, 1/32

A tape or rule marked more coarsely than 64ths can’t show 45/64 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)
1/83/4 in+0.046875+1.191
1/1611/16 in−0.015625−0.397
1/3223/32 in+0.015625+0.397

Drills, plywood and lumber at 45/64 in

Drills either side of 45/64 in
DrillSizeOff by
17.5 mm0.689 in−0.3594 mm
18 mm0.7087 in+0.1406 mm

Every drill is on the drill bit size chart.

Bits of this size

Sizes either side

FractionDecimalmm
11/16 in0.6875 in17.463 mm
23/32 in0.71875 in18.256 mm

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