Calculate recommended clearance hole diameter for metric and inch bolts with close, normal and loose fit options.
The preset values are practical general-purpose estimates. Exact clearance-hole dimensions should be selected from the applicable engineering standard or drawing.
What is a clearance hole? A clearance hole is intentionally larger than the bolt so the bolt passes freely through the material rather than engaging threads.
What is close clearance? A close-clearance hole minimizes the gap around the bolt and is useful where accurate assembly or reduced movement is important.
What is normal clearance? Normal clearance provides a practical gap for general fabrication and easier bolt installation.
What is loose clearance? Loose clearance provides a larger hole, making assembly easier where positional precision is less critical.
Does clearance affect bolt strength? The hole size itself does not change the nominal tensile strength of the bolt, but excessive clearance can affect joint behavior, bearing stresses, slip and alignment.
Should I use the exact calculated value for drilling? For production work, check the applicable standard or engineering drawing. Standard drill sizes may be selected instead of the exact mathematical value.
Can I calculate clearance holes for inch bolts? Yes. Enter the nominal inch diameter and select the desired fit.
Does coating affect clearance holes? Yes. Coatings such as paint, plating or galvanizing can reduce effective hole clearance and may require an appropriate allowance.