Concrete Anchor Pullout Calculator (USA)
Concrete Anchor Pullout CalculatorUSA — ACI 318-19 §17.6.3 · Headed & Hooked Anchors · φNpn Capacity
Calculate the pullout capacity (φNpn) for cast-in headed anchor bolts and hooked J/L-bolts in concrete per ACI 318-19 Section 17.6.3. Includes bearing area calculation, cracked/uncracked concrete factors, demand vs. capacity check, and 2026 USA material cost estimate.
§17.6.3ACI 318-19 Pullout Section
φ=0.70ACI Pullout φ-Factor
ψc,P1.4 Uncracked · 1.0 Cracked
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⚓ Headed Anchor Bolts
🪝 J-Bolt (Hooked)
🔩 L-Bolt (Hooked)
🔘 Headed Stud
🏗️ Column Base Plates
🏠 Sill Plates
Anchor pullout is a brittle failure mode where the anchor pulls straight out of the concrete without fracturing the steel — governed by ACI 318-19 Section 17.6.3. For headed anchors, pullout capacity depends on the net bearing area of the anchor head pressing against the concrete (Np = 8 × Abrg × f’c). For hooked anchors (J-bolts, L-bolts), it depends on the hook extension length and bolt diameter (Np = 0.9 × f’c × eh × da). This free Concrete Anchor Pullout Calculator computes the design pullout capacity φNpn for both anchor types, applies cracked/uncracked concrete modification factors, checks demand vs. capacity, and provides 2026 USA anchor pricing — all per ACI 318-19 Chapter 17.
🧮 Free USA Tool
Anchor Pullout Calculator
φNpn (Pullout Capacity) · Bearing Area · Demand Check · Cost — ACI 318-19 §17.6.3 / 2026 USA
⚓ Headed Anchor
🪝 J/L-Bolt Hooked
🔘 Headed Stud
📐 Cracked / Uncracked
Std hex nut across-flats for 1/2 in bolt ≈ 0.875 in · Heavy hex ≈ 0.969 in
Standard hex nut height for 1/2 in ≈ 0.4375 in · Leave blank to use head dia only
ACI 318-19: 3×da ≤ eh ≤ 4.5×da · For 1/2 in bolt: 1.5–2.25 in
For total quantity and cost estimate
Factored tensile demand per anchor — for demand vs. capacity check
2026 avg: J-bolt 1/2 in $0.80–$1.80 · Headed stud $1.20–$2.50
Design Pullout Capacity (φNpn)
0 lbs
Anchor Pullout — ACI 318-19 §17.6.3 · 2026 USA
📐 Anchor Geometry
⚡ Capacity Breakdown
📋 Demand & Cost
📊 ACI 318-19 §17.6.3 — Pullout Capacity Reference (Headed & Hooked Anchors)
⚓ Headed Anchor — Np Formula (ACI 17.6.3.2)Np = 8 × Abrg × f’c
🪝 Hooked Anchor — Np Formula (ACI 17.6.3.3)Np = 0.9 × f’c × eh × da
🔧 φ-Factor for Pullout (ACI 17.5.3)φ = 0.70
✅ Uncracked Concrete Factor ψc,Pψc,P = 1.4
⚠️ Cracked Concrete Factor ψc,Pψc,P = 1.0
📏 Hooked Anchor eh Limits (ACI 17.6.3.3)3×da ≤ eh ≤ 4.5×da
AbrgNet Bearing Area of Head
8×Headed Bearing Multiplier
0.9×Hook Pullout Coefficient
φNpnDesign Pullout Capacity
What Is Anchor Pullout Capacity?
Anchor pullout is a failure mode where the entire anchor — bolt, head, and all — pulls out of the concrete body as a unit, leaving a clean cylindrical void. It differs from concrete breakout (which fractures a cone of concrete) and steel fracture (which breaks the bolt shank). Per ACI 318-19 Section 17.6.3, pullout capacity is controlled by the mechanical bearing of the anchor head or hook against the surrounding concrete. For headed anchors, a larger head bearing area directly increases pullout resistance — which is why heavy hex nuts or large plate washers are often specified. For hooked J/L-bolts, the hook extension length eh is the primary variable, limited to 3–4.5 times the bolt diameter to prevent the hook from straightening before pullout.
🔑 When Does Pullout Govern Anchor Design?
Pullout most commonly governs when anchors have small head bearing areas (standard hex nuts rather than heavy hex or plate washers), shallow embedment, or low concrete strength. For hooked anchors (J/L bolts), pullout governs when the hook extension eh is at the minimum (3×da) rather than the maximum (4.5×da). The ACI 318-19 design process requires checking all failure modes — steel fracture (§17.6.1), concrete breakout (§17.6.2), pullout (§17.6.3), side-face blowout (§17.6.4), and concrete splitting — and using the lowest (governing) capacity for design. Increasing the head bearing area (e.g. using a 3-inch square plate washer instead of a standard hex nut) is the most economical way to increase pullout capacity without changing anchor size or embedment.
ACI 318-19 §17.6.3 — Pullout Capacity Formulas
📐 Anchor Pullout Capacity Formulas — ACI 318-19 Section 17.6.3
── HEADED ANCHORS (ACI 17.6.3.2) ──
Abrg = (π/4) × (dh² − da²) [Net bearing area of anchor head, in²]
Np = 8 × Abrg × f’c [Nominal pullout strength, lbs]
φNpn = φ × ψc,P × Np = 0.70 × ψc,P × Np
── HOOKED ANCHORS — J/L BOLT (ACI 17.6.3.3) ──
Np = 0.9 × f’c × eh × da [Nominal pullout, lbs · 3da ≤ eh ≤ 4.5da]
φNpn = 0.70 × ψc,P × 0.9 × f’c × eh × da
── MODIFICATION FACTOR ──
ψc,P = 1.4 (uncracked concrete) | ψc,P = 1.0 (cracked concrete)
── DEMAND CHECK ──
Demand Ratio = Nu / φNpn → Must be ≤ 1.0 for adequacy
Pullout Capacity by Anchor Size & Head Type — 2026 Reference
Pullout capacities below are computed per ACI 318-19 §17.6.3.2 for headed anchors in uncracked 3,000 PSI concrete (ψc,P = 1.4, φ = 0.70). Head diameters based on ANSI standard and heavy hex nut dimensions:
| Bolt Dia (da) | Std Hex dh | Abrg (in²) | Np (lbs) | φNpn Uncracked | Heavy Hex dh | φNpn Heavy Hex | 3-in Sq Washer φNpn |
|---|---|---|---|---|---|---|---|
| 3/8 in | 0.653 in | 0.224 | 5,376 | 3,763 lbs | 0.719 in | 4,501 lbs | 11,200 lbs |
| 1/2 in | 0.875 in | 0.405 | 9,720 | 6,804 lbs | 0.969 in | 8,225 lbs | 14,112 lbs |
| 5/8 in | 1.063 in | 0.580 | 13,920 | 9,744 lbs | 1.150 in | 11,088 lbs | 17,640 lbs |
| 3/4 in | 1.250 in | 0.785 | 18,840 | 13,188 lbs | 1.313 in | 14,112 lbs | 21,168 lbs |
| 7/8 in | 1.438 in | 1.017 | 24,408 | 17,086 lbs | 1.516 in | 18,144 lbs | 25,200 lbs |
| 1 in | 1.625 in | 1.276 | 30,624 | 21,437 lbs | 1.719 in | 23,184 lbs | 30,240 lbs |
| 1-1/4 in | 2.063 in | 2.141 | 51,384 | 35,969 lbs | 2.156 in | 36,960 lbs | 46,512 lbs |
🔩 1/2 in — Std Hex Nut
Abrg0.405 in²φNpn (uncracked)6,804 lbsφNpn (heavy hex)8,225 lbsStatusMost Common
🔩 5/8 in — Std Hex Nut
Abrg0.580 in²φNpn (uncracked)9,744 lbsφNpn (heavy hex)11,088 lbs
🔩 3/4 in — Std Hex Nut
Abrg0.785 in²φNpn (uncracked)13,188 lbsφNpn (heavy hex)14,112 lbs
🔩 1 in — Std Hex Nut
Abrg1.276 in²φNpn (uncracked)21,437 lbs3-in Sq Washer30,240 lbs
Hooked Anchor (J-Bolt) Pullout — Hook Length Reference 2026
Pullout capacities for J/L-bolt hooked anchors per ACI 318-19 §17.6.3.3 in uncracked 3,000 PSI concrete (ψc,P = 1.4, φ = 0.70). Hook extension eh limited to 3da–4.5da per ACI:
| Bolt Dia (da) | Min eh (3×da) | φNpn at Min eh | Max eh (4.5×da) | φNpn at Max eh | IRC Req. (7 in embed) | 2026 J-Bolt Price |
|---|---|---|---|---|---|---|
| 3/8 in | 1.125 in | 1,191 lbs | 1.688 in | 1,786 lbs | N/A | $0.40–$0.90 |
| 1/2 in | 1.500 in | 2,835 lbs | 2.250 in | 4,253 lbs | 2.0 in typical | $0.80–$1.80 |
| 5/8 in | 1.875 in | 4,429 lbs | 2.813 in | 6,644 lbs | 2.5 in typical | $1.20–$2.50 |
| 3/4 in | 2.250 in | 6,378 lbs | 3.375 in | 9,568 lbs | 3.0 in typical | $1.80–$3.50 |
| 7/8 in | 2.625 in | 8,680 lbs | 3.938 in | 13,020 lbs | N/A | $2.50–$5.00 |
| 1 in | 3.000 in | 11,340 lbs | 4.500 in | 17,010 lbs | N/A | $3.50–$7.00 |
🪝 1/2 in J-Bolt — Hook Pullout
Min eh (3×da)1.5 in → 2,835 lbsMax eh (4.5×da)2.25 in → 4,253 lbs2026 Price$0.80–$1.80
🪝 5/8 in J-Bolt — Hook Pullout
Min eh (3×da)1.875 in → 4,429 lbsMax eh (4.5×da)2.813 in → 6,644 lbs2026 Price$1.20–$2.50
🪝 3/4 in J-Bolt — Hook Pullout
Min eh (3×da)2.25 in → 6,378 lbsMax eh (4.5×da)3.375 in → 9,568 lbs2026 Price$1.80–$3.50
🔩 How to Increase Pullout Capacity
The most cost-effective way to increase pullout capacity for headed anchors is to increase the head bearing area — upgrading from a standard hex nut (Abrg ≈ 0.405 in² for 1/2-in bolt) to a 3-inch square plate washer (Abrg ≈ 8.64 in²) increases φNpn by more than 20×. For hooked anchors, maximizing the hook extension to 4.5×da doubles capacity compared to 3×da. Increasing concrete strength from 3,000 to 5,000 PSI increases pullout by 67% since Np scales linearly with f’c — unlike breakout which scales with √f’c. These improvements are inexpensive at the design stage but costly to retrofit.
🏠 Sill Plate Anchor Pullout — 2026 IRC
Standard residential 1/2-in × 10-in J-bolts per 2021 IRC R403.1.6 with a 2-inch hook extension in uncracked 3,000 PSI concrete yield φNpn ≈ 3,780 lbs in pullout — well above the typical wind uplift demand per anchor for most one and two-story residential applications. In high-wind zones (ASCE 7-22 Exposure Category D, 130+ mph) or Seismic Design Categories D–F, engineers frequently specify heavier hex nuts or square plate washers and may require hold-down devices (Simpson HDU, Strong-Wall) with rated capacities of 4,000–24,000 lbs specifically tested per ICC-ES ESR-1946 and similar reports.
⚠️ Pullout vs. Breakout — Which Governs?
Both pullout and concrete breakout must be checked — the lower value governs. For shallow embedment with large head area, concrete breakout (§17.6.2) typically governs because the failure cone is small. For deep embedment with small head area, pullout (§17.6.3) governs because the concrete cone is large but the bearing area is insufficient. The crossover point for a 1/2-in bolt in 3,000 PSI concrete with a standard hex nut occurs at approximately hef = 4–5 inches. A complete ACI 318-19 Chapter 17 analysis always checks all five failure modes simultaneously — use the anchor bolt calculator for the full multi-mode check.
⚠️ This Calculator Is for Estimation Only — Licensed Engineer Required for Structural Work
ACI 318-19 Chapter 17 anchor design requires checking all failure modes simultaneously, applying group effect factors for multiple anchors, seismic reduction factors for SDC C–F applications, and concrete cracking assumptions verified by a structural engineer. All permit-required structural anchor designs must be prepared and stamped by a licensed structural or civil engineer. This tool provides educational estimates for planning and preliminary budgeting only. Values assume single anchors without group effects, no supplementary reinforcement, and idealized conditions.
Concrete Anchor Pullout — FAQ
What is the ACI 318-19 pullout formula for headed anchors?+
Per ACI 318-19 Section 17.6.3.2, the nominal pullout strength of a headed anchor bolt is:
- Np = 8 × Abrg × f’c
- Abrg = net bearing area of anchor head = π/4 × (dh² − da²) in square inches
- f’c = concrete compressive strength in PSI
- The factor 8 is an empirical coefficient from full-scale testing of headed anchors
The design pullout capacity is then:
- φNpn = φ × ψc,P × Np
- φ = 0.70 (ACI 17.5.3 — pullout)
- ψc,P = 1.4 for uncracked concrete, 1.0 for cracked concrete
Example: 1/2-in bolt, heavy hex nut (dh = 0.969 in), 3,000 PSI uncracked concrete: Abrg = π/4 × (0.969² − 0.5²) = 0.541 in² → Np = 8 × 0.541 × 3,000 = 12,984 lbs → φNpn = 0.70 × 1.4 × 12,984 = 12,726 lbs.
What is the hook extension limit for J-bolt pullout calculation?+
ACI 318-19 Section 17.6.3.3 limits the hook extension eh used in the pullout formula to:
- Minimum: eh ≥ 3 × da (below this, the hook formula is not valid)
- Maximum: eh ≤ 4.5 × da (above this, no additional pullout credit is given)
For a 1/2-in bolt: 3 × 0.5 = 1.5 in minimum, 4.5 × 0.5 = 2.25 in maximum. Most standard J-bolts are manufactured with a 2-inch hook — which falls within this range. If your J-bolt has a longer hook, you may only use eh = 2.25 in (4.5×da) in the formula. The hook formula only applies to hooked (J or L shape) cast-in anchors — it does not apply to post-installed mechanical or adhesive anchors, which rely on different mechanisms (expansion or bond).
What is the difference between cracked and uncracked concrete for pullout?+
The ψc,P factor in ACI 318-19 §17.6.3.1 accounts for the condition of the concrete at the anchor location:
- Uncracked concrete (ψc,P = 1.4): Concrete at the anchor location is not expected to crack under service load conditions — typical for well-reinforced members, slabs on grade, or foundations below the neutral axis in bending
- Cracked concrete (ψc,P = 1.0): Concrete at the anchor location is expected to crack under service loads — typical for tension zones of beams, near construction joints, poorly reinforced members, or seismic applications (cracks assumed open under seismic loading per ACI)
Using the uncracked assumption adds 40% to pullout capacity but requires engineering justification — in seismic design categories C–F, cracked concrete must always be assumed per ACI 318-19 Section 17.10.5.1, which automatically uses ψc,P = 1.0.
Does a larger concrete strength always increase pullout capacity?+
Yes — unlike concrete breakout (which scales with √f’c), pullout capacity scales linearly with f’c. This means doubling the concrete strength from 3,000 to 6,000 PSI exactly doubles the pullout capacity. Practically:
- 3,000 PSI → 6,000 PSI: pullout capacity ×2.0 (significant improvement)
- 3,000 PSI → 4,000 PSI: pullout capacity ×1.33 (33% improvement)
- 3,000 PSI → 5,000 PSI: pullout capacity ×1.67 (67% improvement)
For concrete breakout (ACI §17.6.2): 3,000 → 6,000 PSI only gives ×1.41 (√2) improvement. This means for pullout-governed anchors, specifying higher strength concrete is more effective than for breakout-governed anchors. That said, the most economical improvement remains increasing the head bearing area with a plate washer rather than upgrading the concrete mix design.
Can I use the pullout formula for post-installed wedge or epoxy anchors?+
No — ACI 318-19 §17.6.3 pullout formulas apply only to cast-in anchors (headed and hooked). Post-installed anchors have different pullout mechanisms:
- Wedge anchors: Pullout is resisted by the mechanical expansion clip bearing against the hole wall — governed by the ICC-ES product report for that specific anchor, not by the ACI bearing area formula. Wedge anchor pullout capacity is determined by testing per ASTM E488 and listed in the ICC-ES ESR report.
- Epoxy/adhesive anchors: Pullout is resisted by bond between the adhesive and the concrete hole wall (bond failure mode, ACI §17.6.5) — calculated using τcr (bond stress) from ICC-ES AC308 testing, completely different from the §17.6.3 formula.
- Concrete screws (Tapcon): Governed entirely by ICC-ES product report — no ACI formula applies.
Always use the manufacturer’s ICC-ES evaluation service report (ESR) for post-installed anchor capacities.
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Trusted References
Standards used for anchor pullout capacity formulas and 2026 USA pricing guidance
🏛️
ACI 318-19 §17.6.3
Design Standard
ACI 318-19 Section 17.6.3 defines the nominal pullout strength formulas for headed and hooked cast-in anchors — the primary source for all pullout capacity calculations in this tool, including the 8×Abrg×f’c and 0.9×f’c×eh×da equations and ψc,P modification factors.
ASTM F1554 — Anchor Rods
Material Standard
ASTM F1554 is the governing US material standard for cast-in anchor rods and bolts in concrete — defining Grades 36, 55, and 105 with their respective yield and tensile strengths. All cast-in anchor bolt specifications in the USA reference this standard.
2021 IRC R403.1.6
Residential Code
IRC Section R403.1.6 establishes minimum anchor bolt requirements for residential sill plates — 1/2-inch diameter, 7-inch embedment, 6-foot spacing — forming the practical baseline for the residential pullout capacity examples provided in this calculator.