Concrete Lintel Calculator (USA)
✅ 2026 ACI 318 / Oberfields Updated
Concrete Lintel Calculator
USA Size, Load, Span, Rebar & Deflection Estimator
Calculate recommended concrete lintel size (4×8 to 12×8), design load, factored moment, shear capacity, maximum allowable deflection, bearing length, rebar schedule, and lintel weight — aligned with 2026 USA ACI 318, Oberfields lintel design guide, and TMS 402 masonry standards for CMU and brick wall openings.
4–12″
Standard USA Lintel Widths (CMU 4″–12″ walls)
8″
Standard Height for All USA Precast Lintels
6″
Min Bearing Each End (USA Code)
Free
No Sign-Up Required
🧱 CMU Block Walls
🪟 Window Openings
🚪 Door Openings
📦 Solid Lintels
🔲 U-Lintels
A concrete lintel is a horizontal structural member placed above a door, window, or other wall opening to carry the load of the masonry and any superimposed loads (floors, roofs) above the opening and transfer it to the supporting masonry on each side. In the USA, concrete lintels are standardized by wall width — available as 4×8, 6×8, 8×8, 10×8, and 12×8 inch precast units in both solid and U-shaped (bond-beam) configurations — and are manufactured to ACI 318 and ASTM A615 Grade 60 rebar specifications. Per the Oberfields Concrete Lintel Design Guide, minimum concrete strength is 3,000–5,000 psi depending on lintel series, and deflection is limited to L/360 ≤ 0.3 inches. Standard minimum bearing is 6 inches each end on the supporting masonry. This free calculator estimates required lintel size, factored design load, moment and shear capacity ratio, deflection, and rebar schedule for any CMU or brick wall opening in the USA.
🧱 Free USA Masonry Tool
Concrete Lintel Calculator
Size · Load · Moment · Shear · Deflection · Rebar · Bearing — 2026 USA ACI 318
📦 Solid & U-Lintels
📐 Apex Load Method
✅ Capacity Ratio
🔩 Rebar Schedule
🪟 Opening & Wall Parameters
Inside face to inside face of masonry support (in)
⬇️ Loading Parameters
Masonry height from top of lintel to next floor/roof
Floor/roof dead load transferred to lintel (lb per linear ft)
Floor/roof live load transferred to lintel (lb per linear ft)
⚙️ Material & Design Spec
Total count for material takeoff
Recommended Lintel Size
— × 8
ACI 318 Apex Load Method · 2026 USA · Oberfields Reference
📐 Lintel Geometry
⬇️ Design Loading
🔩 Rebar & Capacity
📊 Structural Capacity — Demand vs. Capacity Ratios
🧱 Standard USA Concrete Lintel — Anatomy & Key Dimensions
🏗️ Masonry Above (Apex Load Zone)Height above lintel — apex = 0.5 × span, 45° triangle
📦 Concrete Lintel BodyWidth: 3.625″–11.625″ · Height: 7.625″ (standard)
🔩 Rebar (Bottom Tension Zone)1–4 bars Grade 60 ASTM A615 · d = H − 2″ cover
📏 Bearing Zone (Each End)Min 6″ bearing on CMU support each side
↔️ Effective Span L₂Clear span + bearing (center-to-center of supports)
📐 Max Deflectionδ_max = L₂²/360 ≤ 0.3″ (Oberfields / ACI 318)
7.625″
Standard Height — All USA Precast Lintels
6″
Min Bearing Length Each End (USA Code)
5,000
psi f’c — Oberfields Standard Precast
Masonry Above
Lintel Body
Rebar Zone
Bearing Zone
Effective Span
What Is a Concrete Lintel?
A concrete lintel is a precast or cast-in-place reinforced concrete beam installed horizontally above a door, window, garage door, or any other opening in a CMU or brick masonry wall. It serves the same structural role as a steel angle lintel or wood header — spanning the opening and transferring the weight of the masonry and any superimposed loads (floors, roofs) on either side down to the jamb masonry below. In the USA, precast concrete lintels are standardized by the nominal wall width: 4″, 6″, 8″, 10″, and 12″ wide units, all 7.625″ (nominally 8″) tall, manufactured in standard lengths from 16″ to 144″ or custom-cast on site. Two configurations are common: solid lintels (rectangular cross-section, fully precast) and U-lintels (channel-shaped, filled with grout and rebar on site — used in bond beam applications).
🧱 The Apex Load Method — How Lintel Loads Are Calculated in the USA
Per the Oberfields Concrete Lintel Design Guide (ACI 318 basis), when masonry is built continuously above a lintel, the load carried by the lintel is not the full weight of masonry to the next structural level — it is only the triangular “apex” zone formed by 45° lines rising from each end of the opening. This triangle has a height equal to half the effective span (L₂/2) and a base equal to L₂. The equivalent uniform load from this triangular zone is: W_apex = 0.33 × w × L₂ where w = CMU wall weight in psf and L₂ = effective span in feet. If masonry height above the lintel is less than L₂/2, the full masonry height is used instead — the calculator handles both cases automatically.
Design Formulas — ACI 318 Lintel Method
The calculator follows ACI 318-19 flexural and shear design for rectangular reinforced concrete beams, using the Oberfields apex load methodology for masonry load and the standard LRFD load combination (1.2D + 1.6L) for factored design moment and shear:
🧱 Concrete Lintel Design Formulas (ACI 318 / Oberfields)
Effective Span L₂ = Clear Span + Bearing [center-to-center of supports, in inches]
Apex Height h_apex = min(wall_ht_above, L₂/2) [inches]
Masonry Load W_m = (cmu_wt × wall_width / 12) × h_apex / 12 [plf]
Equiv. Apex UDL w_apex = 0.33 × W_m × (L₂/12) [plf, uniform equivalent]
Total Unfact. w_n = w_apex + w_self + w_DL + w_LL [plf]
Factored Load w_u = 1.2 × (w_apex + w_DL + w_self) + 1.6 × w_LL [plf]
Factored Moment Mu = (1/8) × w_u × (L₂/12)² [lb·ft] (simple span)
Factored Shear Vu = (1/2) × w_u × (L₂/12) [lbs]
Mn (capacity) = φ × As × fy × (d − a/2) [lb·ft] where φ=0.9, a=As·fy/(0.85·f’c·b)
Vn (capacity) = φ × (2√f’c × b × d) / 1000 [lbs] where φ=0.75 (ACI 318)
Max Deflection δ_max = L₂² / 360 ≤ 0.3″ (Oberfields / ACI 318)
Standard USA Concrete Lintel Sizes & Self-Weights — 2026
All standard USA precast concrete lintels share the same nominal 7.625″ (8″) height. The width matches the CMU wall. Self-weight per Oberfields and Tidewater Block lintel design guides, grouted solid:
| Lintel Size (W×H) | Actual Width | Eff. Depth d | Self-Weight (plf) | Min f’c | Typical Rebar |
|---|---|---|---|---|---|
| 4×8 (4″ CMU) | 3.625″ | 5.875″ | ~25 lbs/ft | 3,000 psi | 1 × #4 Grade 60 |
| 6×8 (6″ CMU) | 5.625″ | 5.875″ | 33 lbs/ft | 3,000–5,000 psi | 2 × #4 Grade 60 |
| 8×8 (8″ CMU) | 7.625″ | 5.875″ | 50 lbs/ft | 5,000 psi | 2 × #5 Grade 60 |
| 10×8 (10″ CMU) | 9.625″ | 5.875″ | 65 lbs/ft | 5,000 psi | 2 × #5 Grade 60 |
| 12×8 (12″ CMU) | 11.625″ | 5.875″ | 83 lbs/ft | 5,000 psi | 2 × #6 Grade 60 |
| U-Lintel 6×8 | 5.625″ | 5.875″ (grouted) | ~33 lbs/ft | 5,000 psi | 2 × #5 (field placed) |
| U-Lintel 8×8 | 7.625″ | 5.875″ (grouted) | ~50 lbs/ft | 5,000 psi | 2 × #5 (field placed) |
📦 6×8 Solid Lintel (6″ CMU) — Most Common
Actual Width5.625″
Self-Weight33 lbs/ft
Min Concrete3,000–5,000 psi
Rebar2 × #4 Grade 60
📦 8×8 Solid Lintel (8″ CMU)
Actual Width7.625″
Self-Weight50 lbs/ft
Min Concrete5,000 psi
Rebar2 × #5 Grade 60
📦 12×8 Solid Lintel (12″ CMU)
Actual Width11.625″
Self-Weight83 lbs/ft
Min Concrete5,000 psi
Rebar2 × #6 Grade 60
Lintel Load Capacity by Span — USA Reference 2026
Allowable superimposed load (plf) for standard USA precast concrete lintels at common spans — masonry self-weight only (apex zone), no superimposed floor or roof loads. Based on Oberfields and Tidewater Block design capacity tables, 5,000 psi f’c:
| Lintel Size | 3 ft Span | 4 ft Span | 6 ft Span | 8 ft Span | 10 ft Span | Max Span |
|---|---|---|---|---|---|---|
| 4×8 Solid | 900+ plf | 750 plf | 420 plf | 240 plf | — | ~8 ft |
| 6×8 Solid | 1,400+ plf | 1,100 plf | 660 plf | 390 plf | 250 plf | ~10 ft |
| 8×8 Solid | 2,000+ plf | 1,600 plf | 960 plf | 600 plf | 400 plf | ~12 ft |
| 10×8 Solid | 2,500+ plf | 2,000 plf | 1,200 plf | 760 plf | 510 plf | ~14 ft |
| 12×8 Solid | 3,000+ plf | 2,400 plf | 1,450 plf | 920 plf | 620 plf | ~16 ft |
📊 8×8 Lintel — Capacity by Span
4 ft span1,600 plf
6 ft span960 plf
8 ft span600 plf
10 ft span400 plf
📊 6×8 Lintel — Capacity by Span
4 ft span1,100 plf
6 ft span660 plf
8 ft span390 plf
10 ft span250 plf
📏 Lintel Length = Clear Span + 2× Bearing
The overall lintel length (what you order or cast) equals the clear opening span plus the bearing length at each end. With a 72″ clear opening and 6″ bearing each end, you order a 72 + 6 + 6 = 84″ (7 ft) lintel. Standard precast lintels are available in 8″ increments — always round up to the next standard length. Effective span L₂ used in structural calculations is measured center-to-center of the bearing surfaces — for 6″ bearing, L₂ = clear span + 6″ (one full bearing width added). Per Oberfields, this is the span used in all moment, shear, and deflection calculations.
🔩 Solid vs. U-Lintel — When to Use Each
Solid precast lintels are the standard choice for most USA residential and light commercial masonry openings — they arrive fully reinforced and ready to install. U-lintels (channel-shaped bond-beam lintels) are used when the opening is part of a continuous bond beam course in the masonry wall — the U-shape allows reinforcing bars to be threaded through the wall and the unit filled with grout on site, integrating the lintel into the structural masonry system. U-lintels are required by some seismic zone masonry codes and are preferred for walls requiring both lintel and bond beam function at the same course height. Both achieve the same structural performance when properly installed.
⚠️ When to Exceed Standard Lintels
Standard precast lintels are designed for masonry self-weight loads only (apex zone). If your project involves floor or roof loads bearing onto the lintel, large openings over 10 ft, or high seismic zones, the lintel demand will likely exceed standard precast capacity. In these cases, a custom CIP or precast lintel with increased depth (12″, 16″, or 24″) designed by a licensed PE is required. Per ACI 318, any lintel carrying more than the self-weight of masonry in its apex zone should have a project-specific structural calculation — especially for openings exceeding 8 ft in load-bearing walls.
⚠️ Calculator Provides Estimates — PE Review Required for Structural Decisions
This tool applies the ACI 318 / Oberfields apex load methodology to generate preliminary lintel size and capacity estimates for planning and budgeting purposes. For load-bearing walls, high seismic zones, openings over 10 ft, lintels supporting floor or roof framing, or any lintel in a building requiring engineered drawings, a licensed Structural Engineer (SE) or PE must provide a stamped design. Always verify lintel bearing conditions with the masonry contractor and confirm that the selected lintel matches the manufacturer’s load table for the actual installed span and loading conditions before construction.
✅ Concrete Lintel Cost Guide — USA 2026
- 4×8 precast solid lintel (3–4 ft): $15–$35 per lintel
- 6×8 precast solid lintel (4–6 ft): $30–$70 per lintel
- 8×8 precast solid lintel (6–8 ft): $55–$120 per lintel
- 10×8 precast solid lintel (6–8 ft): $75–$160 per lintel
- 12×8 precast solid lintel (8–10 ft): $110–$240 per lintel
- Installation labor: $25–$60 per lintel (2-man crew, typical residential)
- Custom CIP lintel (over 10 ft or heavy load): $150–$500+ per opening including forming, rebar, and concrete
Concrete Lintel — Frequently Asked Questions
How long should a concrete lintel be?+
Lintel length = clear opening + bearing at each end:
- Minimum bearing (USA): 6″ each end — so add 12″ total to clear span
- Heavy loads / long spans: 8″ bearing minimum each end — add 16″ total
- Example: 72″ (6 ft) clear opening → order 72 + 12 = 84″ (7 ft) lintel with 6″ bearing
- Standard stock lengths: Most USA precast suppliers stock in 8″ or 16″ increments (24″, 32″, 40″, 48″, 56″, 64″, 72″, 80″, 88″, 96″, 104″, 112″, 120″, 128″)
- Always round up to the next available standard length — never cut a precast lintel
What size concrete lintel do I need for a 3 ft, 6 ft, and 8 ft opening?+
Standard lintel size recommendations for masonry-only loading:
- 3 ft (36″) opening in 6″ CMU wall: 6×8 solid lintel, 48″ length (6″ bearing each end) — ample capacity
- 6 ft (72″) opening in 8″ CMU wall: 8×8 solid lintel, 84″ length — standard choice for window/door in load-bearing wall
- 8 ft (96″) opening in 8″ CMU wall (garage door): 8×8 solid lintel, 112″ length — verify masonry height in apex zone; add superimposed loads if floor above
- 10 ft (120″) opening: 10×8 or 12×8 solid lintel, 132–136″ — or custom engineered lintel if floor/roof loads present
- When in doubt, go wider/deeper — a slightly oversized lintel is always cheaper than a failed or cracked one
What is the difference between a solid lintel and a U-lintel?+
- Solid lintel: Fully precast rectangular unit, arrives with rebar already installed, ready to place directly in the wall — most common for USA residential and light commercial projects. No field grouting required.
- U-lintel (bond beam lintel): Channel-shaped precast unit with open top, used when the opening course must also serve as a bond beam. Rebar is threaded through on site and the unit is filled with masonry grout to complete the section. Required in some seismic zones and for continuous bond beams per TMS 402.
- Structural performance: When properly grouted and reinforced, U-lintels achieve the same moment and shear capacity as solid lintels of the same size — but field quality control of grouting is critical to achieving design strength.
How is the load on a concrete lintel calculated?+
USA lintel load calculation uses the apex (triangle) load method per Oberfields and ACI 318:
- If masonry above lintel ≥ L₂/2 height: Only the triangular “apex” zone load is carried — equivalent uniform load = 0.33 × w × L₂ (where w = masonry weight psf, L₂ = effective span ft)
- If masonry above lintel is less than L₂/2 height: Full masonry height is used for the triangular load, which is smaller than the full apex
- Superimposed floor/roof loads: Add to the lintel load as uniform dead and live loads in plf — these are in addition to masonry weight
- Factored design load (ACI 318 LRFD): wu = 1.2 × DL + 1.6 × LL
- Design moment: Mu = (1/8) × wu × L₂²
What is the maximum deflection allowed for a concrete lintel?+
Per Oberfields lintel design guide and ACI 318:
- Maximum allowable deflection = L₂²/360, not to exceed 0.3″
- Example: 6 ft effective span → δ_max = (72″)²/360 = 14.4″ — but capped at 0.3″
- Example: 9 ft effective span → δ_max = (108″)²/360 = 32.4″ — capped at 0.3″
- In practice, the 0.3″ cap controls for all spans over roughly 4 ft — the L/360 formula gives a much larger allowance, so deflection for properly sized precast lintels is almost never the governing limit state
- For lintels supporting brittle finishes (tile, plaster), limit deflection to L/480 or consult the finish material manufacturer’s recommendations
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Trusted USA Concrete Lintel Resources
Manufacturer design guides, ACI standards, and sizing references for USA concrete lintel selection and installation.
📦
Oberfields Lintel Design Guide
Manufacturer Reference
Oberfields’ Concrete Lintel Guide provides the authoritative USA design reference for solid and U-lintel load tables, apex load methodology, effective span calculations, bearing requirements, deflection limits, rebar schedules, and ACI 318 design formulas — used by masonry contractors and engineers across the USA for CMU wall lintel selection and verification.
Tidewater Block Lintel Guide
Design Tables
Tidewater Block’s Concrete Lintel Design Guide provides complete load capacity tables for 4×8 through 12×8 solid and U-lintels at all standard spans — including both standard (3,000 psi) and premium (5,000 psi) concrete series design capacities, useful for quick field verification of lintel adequacy for residential and commercial CMU wall openings.
Ernest Maier Lintel Size Guide
Selection Guide
Ernest Maier’s Essential Concrete Lintel Size Guide covers the key considerations for selecting the correct lintel size in USA masonry construction — including load requirements, span measurements, bearing specifications, building code compliance (IBC / ACI 318), and how to interpret manufacturer load tables for both residential and commercial CMU wall applications.