Drill Bit Size Chart
Tools
Data 2026.07.13-audit.1
Checking connection

fractional-inch drill · nominal diameter

21/32
drill bit size.

A 21/32 bit measures 0.6563 in across (16.669 mm).

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

Diameter conversion verified
Calibrated relative diameter · 1 in reference

21/32 · fractional

0.6563 in
16.669 mm
Designation21/32fractional
Inch decimal0.6563nominal
Metric conversion16.669millimetres
Where this size sits from 0 to 1 inch
21/32 · 16.669 mm on a zero to 25.4 millimetre scale. Neighbor marks: 41/64, 43/64.
0 25.4 mm
Show calibrated outline Open in Finder

Where this bit is specified

What 21/32 is for.

21/32 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 21/32.

“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