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Woodworking Math

3/32 inch in decimal and mm

Decimal inches

0.09375 in

0.0938 in to four places

Millimetres

2.38125 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: 3/32 in = 3 ÷ 32 = 0.09375 in.
  2. An inch is exactly 25.4 mm, so 0.09375 × 25.4 = 2.38125 mm, or 2.381 mm to three places.
  3. In feet, divide by 12: 0.09375 ÷ 12 = 0.007813 ft. In centimetres, divide the mm by 10: 0.238125 cm.
  4. The same size in finer steps: 3/32 = 6/64. A tape marked in 16ths, 32nds or 64ths shows it at those marks.

3/32 to the nearest 1/8, 1/16

A tape or rule marked more coarsely than 32ths can’t show 3/32 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)
1/81/8 in+0.03125+0.794
1/161/8 in+0.03125+0.794

Drills, plywood and lumber at 3/32 in

Drills either side of 3/32 in
DrillSizeOff by
2.3 mm0.0906 in−0.0813 mm
2.4 mm0.0945 in+0.0187 mm

Every drill is on the drill bit size chart.

Bits of this size

Sizes either side

FractionDecimalmm
5/64 in0.078125 in1.984 mm
7/64 in0.109375 in2.778 mm

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