number drill · nominal diameter

#4
drill bit size.

A #4 bit measures 0.2090 in across (5.309 mm).

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

Diameter conversion cross-checked

Calibrated relative diameter · 1 in reference

#4 · number

0.2090 in

5.309 mm

Designation#4number

Inch decimal0.2090nominal

Metric conversion5.309millimetres

Where this size sits from 0 to 1 inch

#4 · 5.309 mm on a zero to 25.4 millimetre scale. Neighbor marks: 5.3 mm, #5.

0 25.4 mm

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Measured neighbors

What sits beside #4.

“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

5.3 mmmetric 0.2087 inΔ -0.009 mm 5.4 mmmetric 0.2126 inΔ +0.091 mm 5.2 mmmetric 0.2047 inΔ -0.109 mm 13/64fractional 0.2031 inΔ -0.149 mm 5.5 mmmetric 0.2165 inΔ +0.191 mm

Same seriesNEAREST NOMINAL ROWS

#5number 5.220 mmΔ -0.089 mm #3number 5.410 mmΔ +0.102 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

#4drill bit size.

What sits beside #4.

ASME.

#4
drill bit size.