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Woodworking Math

7/32 inch in decimal and mm

Decimal inches

0.21875 in

0.2188 in to four places

Millimetres

5.55625 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: 7/32 in = 7 ÷ 32 = 0.21875 in.
  2. An inch is exactly 25.4 mm, so 0.21875 × 25.4 = 5.55625 mm, or 5.556 mm to three places.
  3. In feet, divide by 12: 0.21875 ÷ 12 = 0.018229 ft. In centimetres, divide the mm by 10: 0.555625 cm.
  4. The same size in finer steps: 7/32 = 14/64. A tape marked in 16ths, 32nds or 64ths shows it at those marks.

7/32 to the nearest 1/8, 1/16

A tape or rule marked more coarsely than 32ths can’t show 7/32 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)
1/81/4 in+0.03125+0.794
1/161/4 in+0.03125+0.794

Drills, plywood and lumber at 7/32 in

Drills either side of 7/32 in
DrillSizeOff by
5.5 mm0.2165 in−0.0563 mm
5.6 mm0.2205 in+0.0437 mm

Every drill is on the drill bit size chart.

Bits of this size

Sizes either side

FractionDecimalmm
13/64 in0.203125 in5.159 mm
15/64 in0.234375 in5.953 mm

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