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Woodworking Math

1/32 inch in decimal and mm

Decimal inches

0.03125 in

0.0313 in to four places

Millimetres

0.79375 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: 1/32 in = 1 ÷ 32 = 0.03125 in.
  2. An inch is exactly 25.4 mm, so 0.03125 × 25.4 = 0.79375 mm, or 0.794 mm to three places.
  3. In feet, divide by 12: 0.03125 ÷ 12 = 0.002604 ft. In centimetres, divide the mm by 10: 0.079375 cm.
  4. The same size in finer steps: 1/32 = 2/64. A tape marked in 16ths, 32nds or 64ths shows it at those marks.

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

A tape or rule marked more coarsely than 32ths can’t show 1/32 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)
1/80 in−0.03125−0.794
1/161/16 in+0.03125+0.794

Drills, plywood and lumber at 1/32 in

Drills either side of 1/32 in
DrillSizeOff by
0.7 mm0.0276 in−0.0938 mm
0.8 mm0.0315 in+0.0063 mm

Every drill is on the drill bit size chart.

Sizes either side

FractionDecimalmm
1/64 in0.015625 in0.397 mm
3/64 in0.046875 in1.191 mm

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