Skip to content
Woodworking Math

39/64 inch in decimal and mm

Decimal inches

0.609375 in

0.6094 in to four places

Millimetres

15.478125 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: 39/64 in = 39 ÷ 64 = 0.609375 in.
  2. An inch is exactly 25.4 mm, so 0.609375 × 25.4 = 15.478125 mm, or 15.478 mm to three places.
  3. In feet, divide by 12: 0.609375 ÷ 12 = 0.050781 ft. In centimetres, divide the mm by 10: 1.5478125 cm.

39/64 to the nearest 1/8, 1/16, 1/32

A tape or rule marked more coarsely than 64ths can’t show 39/64 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
1/325/8 in+0.015625+0.397

Drills, plywood and lumber at 39/64 in

Drills either side of 39/64 in
DrillSizeOff by
15 mm0.5906 in−0.4781 mm
15.5 mm0.6102 in+0.0219 mm

Every drill is on the drill bit size chart.

Bits of this size

Sizes either side

FractionDecimalmm
19/32 in0.59375 in15.081 mm
5/8 in0.625 in15.875 mm

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