Other naming systemsABSOLUTE DIAMETER DELTA
fractional-inch drill · nominal diameter
51/64
drill bit size.
A 51/64 bit measures 0.7969 in across (20.241 mm).
The fractional diameter is exact; decimal and metric values are conversions.
Calibrated relative diameter · 1 in reference
51/64 · fractional
0.7969 in
20.241 mm Designation51/64fractional
Inch decimal0.7969nominal
Metric conversion20.241millimetres
Where this size sits from 0 to 1 inch 51/64 · 20.241 mm on a zero to 25.4 millimetre scale. Neighbor marks: 25/32, 13/16.
Measured neighbors
What sits beside 51/64.
“Nearest” means nominal diameter only. It does not make a neighboring size acceptable for a tolerance, tapping, reaming, or fastener application.
Source record
Drill Bit Size Chart.
Fractional sizes are exact rational multiples of one inch.
Open source record