1-3/8 inch in decimal and mm
Decimal inches
1.375 in
Millimetres
34.925 mm
From the standard, the international inch, 25.4 mm exactly
The math
- A fraction is its top number divided by its bottom number: 1-3/8 in = 1 + 3 ÷ 8 = 1.375 in.
- An inch is exactly 25.4 mm, so 1.375 × 25.4 = 34.925 mm.
- In feet, divide by 12: 1.375 ÷ 12 = 0.114583 ft. In centimetres, divide the mm by 10: 3.4925 cm.
- The same size in finer steps: 1-3/8 = 1-6/16 = 1-12/32 = 1-24/64. A tape marked in 16ths, 32nds or 64ths shows it at those marks.
Drills, plywood and lumber at 1-3/8 in
No drill, plywood or lumber on our charts is exactly 1-3/8 in. The nearest drills are below.
| Drill | Size | Off by |
|---|---|---|
| 1 in | 1 in | −0.375 in |
| 25 mm | 0.9843 in | −9.925 mm |
Every drill is on the drill bit size chart.
Bits of this size
Sizes either side
Every size is on the fraction to decimal chart; any other size goes in the fraction to decimal calculator.