Drill Bit Size Chart
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Data 2026.07.13-audit.1
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fractional-inch drill · nominal diameter

13/16
drill bit size.

A 13/16 bit measures 0.8125 in across (20.637 mm).

The fractional diameter is exact; decimal and metric values are conversions.

Diameter conversion verified
Calibrated relative diameter · 1 in reference

13/16 · fractional

0.8125 in
20.637 mm
Designation13/16fractional
Inch decimal0.8125nominal
Metric conversion20.637millimetres
Where this size sits from 0 to 1 inch
13/16 · 20.637 mm on a zero to 25.4 millimetre scale. Neighbor marks: 53/64, 51/64.
0 25.4 mm
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Where this bit is specified

What 13/16 is for.

13/16 is the cutting-tap drill for the thread below— usually the reason this size gets looked up. Engagement is calculated from the basic 60° profile; open a thread for its published row, evidence, and limits.

Measured neighbors

What sits beside 13/16.

“Nearest” means nominal diameter only. It does not make a neighboring size acceptable for a tolerance, tapping, reaming, or fastener application.

Other naming systemsABSOLUTE DIAMETER DELTA

Source record

Drill Bit Size Chart.

Fractional sizes are exact rational multiples of one inch.

Open source record