By Zencalcy Editorial TeamLast reviewed About us
A clearance hole must be larger than the fastener, but not so large that the head pulls through or the joint slips. The usual rule is bolt diameter plus 1/16 inch for a normal fit, plus 1/32 for close and plus 1/8 for loose. Metric fits follow ISO 273.
Drill the right clearance hole for a bolt or screw.
close = d + 1/32 in normal = d + 1/16 in loose = d + 1/8 in
Metric ISO 273 gives, for an M10 bolt, 10.5 mm close, 11 mm normal and 12 mm loose. For wood screws, add about 1/16 inch to the shank diameter, not the thread diameter.
| Symbol | Meaning |
|---|---|
| d | Fastener diameter. |
| D | Clearance hole diameter. |
0.5 + 0.0625 = 0.5625 inch, so a 9/16 inch hole or a 14 mm drill.
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13/32 inch for a close fit, 7/16 inch for normal, and 1/2 inch for a loose fit.
Results use standard construction estimating arithmetic: volumes from measured area and depth, unit weights from published material densities, and code-referenced spans or clearances where the page names a code. Quantities are rounded up to whole saleable units and include the stated waste allowance. These tools are planning aids, not structural design, and do not replace a licensed engineer, a local code check, or a contractor's site measurement.
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Last reviewed: September 2026. See how we build and check every tool on the about page.
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Content updated: September 2026