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Woodworking Math

25/32 inch in decimal and mm

Decimal inches

0.78125 in

0.7813 in to four places

Millimetres

19.84375 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: 25/32 in = 25 ÷ 32 = 0.78125 in.
  2. An inch is exactly 25.4 mm, so 0.78125 × 25.4 = 19.84375 mm, or 19.844 mm to three places.
  3. In feet, divide by 12: 0.78125 ÷ 12 = 0.065104 ft. In centimetres, divide the mm by 10: 1.984375 cm.
  4. The same size in finer steps: 25/32 = 50/64. A tape marked in 16ths, 32nds or 64ths shows it at those marks.

25/32 to the nearest 1/8, 1/16

A tape or rule marked more coarsely than 32ths can’t show 25/32 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)
1/83/4 in−0.03125−0.794
1/1613/16 in+0.03125+0.794

Drills, plywood and lumber at 25/32 in

Drills either side of 25/32 in
DrillSizeOff by
19.5 mm0.7677 in−0.3438 mm
20 mm0.7874 in+0.1563 mm

Every drill is on the drill bit size chart.

Bits of this size

Sizes either side

FractionDecimalmm
49/64 in0.765625 in19.447 mm
51/64 in0.796875 in20.241 mm

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