-------- | -------------- | --------------- | ------------------ | --------------- | | 1/2 | 9/16 | 5/8 | 9/16 × 11/16 | 9/16 × 1-1/4 | | 5/8 | 11/16 | 13/16 | 11/16 × 7/8 | 11/16 × 1-9/16 | | 3/4 | 13/16 | 15/16 | 13/16 × 1 | 13/16 × 1-7/8 | | 7/8 | 15/16 | 1-1/16 | 15/16 × 1-1/8 | 15/16 × 2-3/16 | | 1 | 1-1/16 | 1-1/4 | 1-1/16 × 1-5/16 | 1-1/16 × 2-1/2 | | 1-1/8 | d + 1/16 | d + 5/16 | (d+1/16) × (d+3/8) | (d+1/16) × 2.5d | | 1-1/4 | d + 1/16 | d + 5/16 | (d+1/16) × (d+3/8) | (d+1/16) × 2.5d | | 1-3/8 | d + 1/16 | d + 5/16 | (d+1/16) × (d+3/8) | (d+1/16) × 2.5d | | 1-1/2 | d + 1/16 | d + 5/16 | (d+1/16) × (d+3/8) | (d+1/16) × 2.5d |

Most searched: a 3/4 in bolt has a standard hole of 13/16 in (0.8125 in). This 1/16 in clearance per side provides standard erection tolerance. A 7/8 in bolt uses a 15/16 in standard hole.

Formula-Based Sizes (for bolts 1-1/8 in and larger)

The 1/16 in clearance above bolt diameter for standard holes is consistent across all bolt sizes. The 5/16 in oversized clearance provides significantly more fit-up tolerance at the cost of reduced slip resistance.

Hole Type Selection Guide

Standard Holes (STD) — The Default Choice

Standard holes provide the minimum clearance needed for bolt installation under normal conditions. Use them unless a specific design reason requires a larger hole.

• Where permitted: All connection types — bearing-type and slip-critical
• Slip resistance factor: h_sc = 1.0 (full slip resistance)
• Bearing coefficient: 2.4d (full bearing strength)
• Net area deduction: d + 1/8 in (hole + 1/16 in damage allowance)
• When to use: Default for all connections; best for tension members (minimizes net area reduction)

Oversized Holes (OVS) — Extra Fit-Up Tolerance

Oversized holes provide additional clearance to accommodate accumulated erection tolerances, especially in multi-story frames.

• Where permitted: Slip-critical connections only (AISC 360 Section J3.2)
• Slip resistance factor: h_sc = 0.85
• Bearing coefficient: 2.0d (reduced from 2.4d)
• Plate washers: Required over OVS holes in any outer ply
• When to use: Multi-story beam-to-column connections, long-span splices, connections to concrete with anchor bolt tolerance issues

Short-Slotted Holes (SSL) — One-Direction Adjustment

Short-slotted holes allow approximately one bolt diameter of linear adjustment in one direction.

• Where permitted: Bearing-type and slip-critical connections
• Slip resistance factor (slot ⊥ to load): h_sc = 0.85
• Slip resistance factor (slot ∥ to load): h_sc = 0.70
• Bearing coefficient: 2.0d
• When to use: Beam web connections (slot perpendicular to beam axis), brace connections requiring field adjustment

Long-Slotted Holes (LSL) — Movement Accommodation

Long-slotted holes allow up to approximately 2.5 bolt diameters of movement for thermal expansion, settlement, or ongoing structural movement.

• Where permitted: Slip-critical connections only
• Slip resistance factor (slot ⊥ to load): h_sc = 0.85
• Slip resistance factor (slot ∥ to load): h_sc = 0.70
• Bearing coefficient: 2.0d (load parallel); 1.0 Lc (load perpendicular, no bearing limit)
• Plate washers: Required over LSL holes in any outer ply
• When to use: Expansion joints, connections to concrete with expected settlement, bridge expansion bearings

Net Area Deduction per AISC 360 Section J3.2

For net area calculations in tension members, the hole deduction is:

Hole deduction = hole diameter + 1/16 in    (for punched or drilled holes)

The extra 1/16 in accounts for material damage around the hole edge from the punching process. Examples for common bolt sizes:

Example: For a 3/4 in bolt through a 1/2 in plate, the net area deduction is 7/8 in × 1/2 in = 0.438 in² per hole. For a tension member with 4 bolts in one cross-section, the total net area reduction = 4 × 0.438 = 1.75 in².

Slip Resistance Reduction Factors (AISC 360 Table J3.1)

The nominal slip resistance per bolt is:

Rn = mu × Du × h_sc × h_f × T_b × n_s

Where mu = mean slip coefficient (0.30–0.50), Du = 1.13 (ratio of mean to specified pretension), h_sc = hole factor from table above, h_f = fill factor (1.0 for one fill plate, 0.85 for two or more), T_b = minimum fastener pretension, n_s = number of slip planes.

Bearing Strength by Hole Type

AISC 360 Section J3.10 defines bearing strength depending on hole type:

Standard holes:

Rn = 1.2 × Lc × t × Fu    (tearout governs)
Rn = 2.4 × d × t × Fu     (deformation limit governs)

Oversized and slotted holes:

Rn = 1.0 × Lc × t × Fu    (tearout, reduced coefficient)
Rn = 2.0 × d × t × Fu     (bearing, reduced coefficient)

Long-slotted holes with load perpendicular to slot:

Rn = 1.0 × Lc × t × Fu    (tearout only — no bearing deformation limit)

Connection Design Checklist by Hole Type

*SSL holes in bearing-type connections are permitted when slot is perpendicular to load. †SSL holes in outer ply may require washers depending on orientation.

Quick Reference: Most Common Values

Frequently Asked Questions

What is the standard hole size for a 3/4 in bolt? A 3/4 in diameter bolt uses a standard (STD) hole of 13/16 in (0.8125 in) per AISC 360-22 Table J3.3. The 1/16 in oversize provides clearance for bolt installation. For net area calculations, deduct 7/8 in per hole (standard hole diameter + 1/16 in damage allowance).

Can oversized holes be used in bearing-type connections? No. Oversized holes are only permitted in slip-critical connections per AISC 360 Section J3.2. Bearing-type connections require direct contact between bolt and connected part, which oversized clearance prevents. Using OVS holes in a bearing-type connection would require the bolt to travel too far before engaging bearing.

What is the slip resistance penalty for slotted holes? Short-slotted holes perpendicular to load: h_sc = 0.85 (15% reduction). Short-slotted holes parallel to load: h_sc = 0.70 (30% reduction). Long-slotted holes follow the same factors: 0.85 perpendicular, 0.70 parallel. Standard holes have no reduction (h_sc = 1.0).

When are plate washers required for bolt holes? Plate washers (or a single structural washer covering the full hole) are required in any outer ply containing oversized (OVS) or long-slotted (LSL) holes. This prevents the bolt head or nut from pulling into the oversized opening under load. Short-slotted holes in outer plies may not require washers in all cases — check AISC 360 Section J3.2 for the specific exception.

What is the bearing strength difference between standard and oversized holes? Standard holes use 2.4 × d × t × Fu for the bearing deformation limit. Oversized and slotted holes use 2.0 × d × t × Fu — a 17% reduction. For tearout, standard holes use 1.2 × Lc × t × Fu while oversized/slotted holes use 1.0 × Lc × t × Fu — a 17% reduction in the tearout coefficient.

Try it now: Check your bolt hole sizes with our free Bolted Connection calculator →

Related Pages

• Bolt Spacing & Edge Distance Reference
• Bolt Capacity Table — A325 & A490 Shear and Tension
• Bolted Connections Calculator
• Steel Fy & Fu Table
• Bolt Torque Chart
• Weld Joint Types
• Steel Connection Design
• Base Plate & Anchors Calculator

Educational reference only. Verify against AISC 360-22 Table J3.3 and governing project specification.

Design Resources

Calculator tools

• Bolt Torque Calculator
• Bolted Connection Calculator
• Splice Connection Calculator
• Steel Bolted Connection Calculator

Design guides

• Bolt Torque Worked Example
• Bolted Connection Checklist
• Bolted Connection Worked Example
• AISC Shear Tab Example
• EN 1993-1-8 Bolted Connection Worked Example