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

7/8
drill bit size.

A 7/8 bit measures 0.8750 in across (22.225 mm).

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

Diameter conversion verified
Calibrated relative diameter · 1 in reference

7/8 · fractional

0.8750 in
22.225 mm
Designation7/8fractional
Inch decimal0.8750nominal
Metric conversion22.225millimetres
Where this size sits from 0 to 1 inch
7/8 · 22.225 mm on a zero to 25.4 millimetre scale. Neighbor marks: 55/64, 57/64.
0 25.4 mm
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Where this bit is specified

What 7/8 is for.

7/8 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 7/8.

“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