Clearance Hole Calculator

All construction tools

Determine the correct drill bit size for bolt and screw clearance holes based on fit standards.

Fastener Details

Bolt System

Bolt Size

Fit Classification

Specified Hole Dimensions

Select fastener details to see results

About this calculator

Overview

A clearance hole is a hole drilled through a material that is large enough to allow the shank of a fastener to pass through without threading. The size of the hole depends on the desired 'fit'—ranging from tight tolerances for precision assembly to loose tolerances for easy alignment.

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Pro Tips

Use a 'Normal Fit' for most general engineering applications.
For wood projects, you may want a tighter fit to ensure the screw grabs the material effectively if not using a pilot hole in the second piece.
Check your drill bit set for the closest available size to the calculated diameter.

Fun Facts

"ISO 273 is the international standard for metric clearance holes."
"A 'Close Fit' is typically used when precise location is required."
"A 'Loose Fit' allows for more variation in hole placement and easier assembly."

Formula: Hole Diameter = Nominal Bolt Diameter + Clearance Factor