What this page answers

Pick a bolt diameter and the thickness of the thinner connected part, and you get the hole sizes, the minimum edge distance, the minimum and preferred spacing, and the two maximums that depend on thickness. Each answer shows the arithmetic and names the AISC 360 section it comes from, so it can be checked rather than trusted.

Where each number comes from

Answer	Rule used	Section
Standard hole	d + 1/16 below 1" diameter; d + 1/8 at 1" and larger	Table J3.3
Oversized hole	d + 1/8 at 1/2"; d + 3/16 from 5/8" to 7/8"; d + 1/4 at 1"; d + 5/16 at 1 1/8" and larger	Table J3.3
Short-slot	standard width (so it widens at 1" too); length d + 3/16 at 1/2", d + 1/4 from 5/8" to 7/8", d + 5/16 at 1", d + 3/8 above	Table J3.3
Long-slot	standard width; length 2.5 d	Table J3.3
Minimum edge distance	the tabulated value for the diameter; 1.25 d above 1 1/4"	Table J3.4
Maximum edge distance	12 t, but never more than 6"	J3.5
Minimum spacing	2 2/3 d, rounded up to the next 1/16	J3.3
Preferred spacing	3 d	J3.3
Maximum spacing, painted or not subject to corrosion	24 t, but never more than 12"	J3.5
Maximum spacing, unpainted weathering steel	14 t, but never more than 7"	J3.5

One change that catches people out

The 15th edition widened the standard hole for bolts 1 in. and larger, from d + 1/16 to d + 1/8. A 1" bolt now takes a 1 1/8" standard hole, and the short- and long-slot widths widened with it. A chart printed before that change shows 1 1/16", and plenty of them are still pinned above desks. If your shop standard says 1 1/16" for a 1" bolt, it predates the 15th edition — that is a conversation with your fabricator, not a typo on this page.

The values here were checked against the RCSC Specification for Structural Joints Using High-Strength Bolts (June 11, 2020), Table 3.1 — the primary document AISC's Table J3.3 mirrors — and its commentary, which states the clearance increase for 1-in.-and-larger bolts in as many words.

What it will not do

• It does not size the bolt, check bearing, tearout, slip or block shear. It is geometry, not capacity.
• It does not know your hole is slotted across the load, or that the edge is a sheared edge on a plate that also carries the tension. Both change what a checker will accept.
• It has no workable-gage table. Gages depend on the shape and belong with a shape lookup, not here.
• Slotted holes need edge distance measured to the end of the slot, plus the increase the spec requires. The card says so; it does not compute it for you.
• The spec governs, and your project may be stricter. Fabricator standards routinely are.

Checking it yourself

The one everybody knows: a 3/4" bolt gets a 13/16" standard hole, 1" minimum edge distance, and 2 1/4" preferred spacing. If this page ever says otherwise, do not use it — tell us.

Where these numbers were checked

• Hole sizes — RCSC Specification for Structural Joints Using High-Strength Bolts, June 11, 2020, Table 3.1 and its commentary (the primary document behind AISC Table J3.3).
• Minimum edge distance — two independent sources that agree line for line, plus the note that the pre-2010 table carried a second, larger column for sheared edges which the 2010 Specification removed. The values here are the single current column.
• Spacing and the maximums — AISC 360 J3.3 and J3.5, confirmed in two places including a direct quotation of the J3.5 text.
• Every one of those is a published reference, not a memory. Where two sources disagreed, the primary document decided it — and in one case that is exactly how the 1" hole size above got corrected.