Clearance Hole Calculator
Determine the correct clearance hole size for your bolts and screws to ensure proper fit and easy assembly. Select from close, normal, or loose fit classifications based on your alignment requirements.
Nominal thread diameter of the bolt or screw
Optional — affects clearance recommendation if over 1/2"
Optional — used to verify head clearance
Dhole = Dthread + (Dthread x CF)
Clearance Factors (CF):
Close Fit: +10%
Normal Fit: +15%
Loose Fit: +25%
Practical result rounded up to nearest 1/64″
Hole = 0.5000 + (0.5000 x 0.15)
Hole = 0.5000 + 0.0750
Hole = 0.5750″
Rounded to nearest 1/64″: 5/8″ (0.6250″)
Total clearance: ~0.050″ per side
What is the difference between close, normal, and loose fit clearance holes?
Close fit provides the smallest clearance and is used when precise alignment is critical, such as in jigs and fixtures. Normal fit is suitable for most general assembly and structural applications. Loose fit provides extra clearance and is used when alignment is less critical or when quick assembly is needed, such as in field repairs.
What clearance hole size do I need for a 1/2-13 bolt?
For a standard 1/2-13 bolt, the recommended clearance hole sizes are: close fit = 9/16" (0.5625"), normal fit = 5/8" (0.6250"), and loose fit = 11/16" (0.6875"). Always add 1/16" minimum clearance for general assembly work.
Does material thickness affect clearance hole size?
Yes, in thicker materials you may need slightly larger clearance to account for drill bit wander and bolt misalignment. For materials over 1/2" thick, consider using the next larger clearance class. For materials under 1/8" thick, you can typically use a close fit.
Should clearance holes be tapped or threaded?
No, clearance holes should NOT be threaded. A clearance hole is intentionally oversized to allow the bolt or screw to pass through freely without engaging the threads in the hole. The threads engage only in the nut or threaded receiver on the opposite side.
🔗 Related Calculators
📐 Formula
Dhole = Dthread + (Dthread x CF)
Clearance Factors (CF):
Close Fit: +10%
Normal Fit: +15%
Loose Fit: +25%
Practical result rounded up to nearest 1/64″
📝 Example Calculation
Hole = 0.5000 + (0.5000 x 0.15)
Hole = 0.5000 + 0.0750
Hole = 0.5750″
Rounded to nearest 1/64″: 5/8″ (0.6250″)
Total clearance: ~0.050″ per side