number drill · nominal diameter

#3
drill bit size.

A #3 bit measures 0.2130 in across (5.410 mm).

The inch decimal is the published nominal designation; millimetres are a conversion.

Diameter conversion cross-checked

Calibrated relative diameter · 1 in reference

#3 · number

0.2130 in

5.410 mm

Designation#3number

Inch decimal0.2130nominal

Metric conversion5.410millimetres

Where this size sits from 0 to 1 inch

#3 · 5.410 mm on a zero to 25.4 millimetre scale. Neighbor marks: 5.4 mm, 5.5 mm.

0 25.4 mm

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Measured neighbors

What sits beside #3.

“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

5.4 mmmetric 0.2126 inΔ -0.010 mm 5.5 mmmetric 0.2165 inΔ +0.090 mm 5.3 mmmetric 0.2087 inΔ -0.110 mm 7/32fractional 0.2188 inΔ +0.146 mm 5.6 mmmetric 0.2205 inΔ +0.190 mm

Same seriesNEAREST NOMINAL ROWS

#4number 5.309 mmΔ -0.102 mm #5number 5.220 mmΔ -0.191 mm

Source record

ASME.

The standard text is paywalled. Number and letter series are cross-checked against public manufacturer charts; exact standard edition/page verification remains a release gate.

Open source record

#3drill bit size.

What sits beside #3.

ASME.

#3
drill bit size.