🔩 Clearance Hole Calculator
Find the recommended clearance hole diameter for a bolt or screw of a given size, for close, normal, or loose fits.
What This Calculator Does
A clearance hole is a hole sized slightly larger than a bolt or screw’s shank so the fastener passes through freely without threading into that piece. This calculator suggests a clearance hole size based on common fit classes.
The Method
Standard machinery’s-handbook style guidance scales the hole diameter as a percentage above the nominal fastener diameter: roughly +5% for a close fit (minimal wobble, precise alignment), +10% for a normal/free fit (typical general assembly), and +20% for a loose fit (easy assembly, more misalignment tolerance).
These percentages approximate common reference tables (such as ANSI/ISO clearance hole charts) but exact standard hole sizes are usually rounded to a standard drill bit size. Always check the specific standard drill size chart for your fastener size and fit class before machining critical parts.