TryBuildCalcWindow Lintel CalculatorLintel estimator for window openings
Calculate concrete, steel, and shuttering quantity for an RCC lintel over a door or window opening.
🕒 Last updated: July 4, 2026
Basic Dimensions
ℹ️Clear width of the door/window opening, not the lintel's own length.
ℹ️Commonly 150 mm minimum on each side for typical openings — confirm against your project's structural drawing.
ℹ️A lintel normally spans the full wall thickness.
ℹ️Rule of thumb: span ÷ 10 to span ÷ 12, with a practical minimum of ~150 mm.
ℹ️Set to more than 1 if several openings share the same lintel size.
Material Details
Reinforcement
ℹ️Commonly 100-150 mm centre-to-centre for residential lintels.
Cost
For 1 lintel of 1.50 m (4.92 ft) each (span + bearing), you need approximately 0.054 m³ of concrete and 4.9 kg of reinforcement steel.
Concrete
Concrete volume: 0.054 m³ (1.92 cft)
Cement: 0.4 bags
Sand: 0.023 m³ (0.81 cft)
Aggregate: 0.046 m³ (1.61 cft)
Steel Reinforcement
Main (Bottom) Bars: 2 × 10 mm
Stirrups: 11 × 8 mm
Total steel weight: 4.9 kg
Shuttering
Soffit area: 0.35 m²
Side faces: 0.45 m²
Total contact area: 0.79 m² (8.6 sqft)
| Bar Type | Diameter | Count / Spacing | Cutting Length | Total Length | Weight |
|---|---|---|---|---|---|
| Main (Bottom) Bars | 10 mm | 2 | 1.450 m | 2.90 m | 1.79 kg |
| Stirrups | 8 mm | 150 mm c/c (11/lintel) | 0.720 m | 7.92 m | 3.13 kg |
Assumptions Used
Lintel length = clear span + bearing on both sides | Steel weight: d² ÷ 162 (kg/m) | Stirrup hook allowance: 10 × diameter per end | Concrete dry volume factor: 1.54
Approximate results for planning only. Verify with a professional.
Unsure about bearing length or depth for your opening span? Lintel Design Guide →
Diagram simplified for clarity (not to scale). Illustrative only.
What Is a Lintel Calculator?
A lintel is the small reinforced concrete beam placed directly above a door or window opening to carry the masonry (and often slab) load above it safely down to the solid wall on either side. This calculator estimates everything needed to cast one — concrete volume and cement bags, the steel bar schedule (main bars, top hanger bars, and stirrups) with total weight, and the shuttering (formwork) contact area — from the opening span, bearing length, lintel size, and reinforcement you enter.
It's built for the standard, everyday case: one RCC lintel over one door or window opening in ordinary residential and small commercial construction — the bridge between the masonry work around an opening and the RCC work of the lintel itself.
What makes this calculator different:
Most lintel tools give you a fragmented result — a load calculation here, a cost estimate there. This calculator combines concrete, steel, and shuttering into one result using the same underlying formulas as this site's dedicated concrete, steel, and shuttering calculators, so you don't need to re-enter the same dimensions three times.
Applicable standards:
- Bearing length and depth rules of thumb used here are commonly cited conventions (some referenced in codes such as IS 456), not a single universal standard — always confirm against your project's applicable structural code.
- Opening size, lintel size, and reinforcement must come from the approved architectural/structural drawing for anything beyond routine, lightly loaded openings.
- This calculator estimates material quantity only, not structural design (load, bending, shear, or deflection checks).
How Is the Lintel Quantity Calculated?
The calculation happens in four parts — lintel length, concrete quantity, steel reinforcement, and shuttering area — then an optional cost estimate on top.
Step 1 — Lintel Length
Lintel Length = Opening Span + (2 × Bearing Length)
The lintel must rest on solid wall beyond the opening on both sides — its true length is always longer than the opening it spans.
Step 2 — Concrete Volume
Wet Volume = Length × Width × Depth (per lintel, × count for multiple openings)
Dry Volume = Wet Volume × 1.54
Cement Bags = Cement Volume ÷ 0.0347 m³/bag (50 kg bags)
Dry volume accounts for the voids between aggregate particles that disappear once the concrete is mixed and compacted. The dry volume is then split into cement, sand, and aggregate using the selected mix ratio, and the wastage percentage is applied once to the final quantities.
Step 3 — Steel Reinforcement
Bar Length (each bar) = Lintel Length − (2 × Concrete Cover)
Stirrups per Lintel = ⌊(Lintel Length ÷ Spacing)⌋ + 1
Stirrup Cutting Length = 2 × (Width − 2×Cover + Depth − 2×Cover) + Hook Allowance (2 × 10 × diameter)
Unit Weight (kg/m) = Diameter² ÷ 162
Main and top bars run the length of the lintel minus end cover; stirrups are closed loops sized to the concrete section minus cover on each side, with a hook allowance added at both ends to close the loop.
Step 4 — Shuttering Area
Soffit Area = Width × Length
Side Area = 2 × Depth × Length
Total Contact Area = (Soffit + Side Area) × Count
Shuttering supports the underside (soffit) and both vertical faces of the lintel until the concrete gains enough strength to be self-supporting — the wall itself typically forms the end shuttering, so no separate end panels are counted.
Worked Example
This example walks through your current inputs above, using the same steps as the Formula section.
Step 1 — Lintel Length
| Calculation | Substitution | Result |
|---|---|---|
| Opening span | 1.2 m | 1.200 m |
| Bearing (each side) | 150 mm | 0.150 m |
| Lintel length | 1.200 + 2 × 0.150 | 1.500 m (4.92 ft) |
Step 2 — Concrete
| Calculation | Substitution | Result |
|---|---|---|
| Wet volume | 1.50 × 230mm × 150mm × 1 | 0.052 m³ |
| With 5% wastage | 0.052 × 1.05 | 0.054 m³ (0.4 bags) |
Step 3 — Steel
| Bar Type | Substitution | Weight |
|---|---|---|
| Main (Bottom) Bars | 2 × 1.450 m × 10²÷162 | 1.79 kg |
| Stirrups | 11 × 0.720 m × 8²÷162 | 3.13 kg |
| Total steel | Sum of all rows | 4.92 kg |
Therefore, 1 lintel of 1.50 m each needs 0.054 m³ of concrete, 4.9 kg of steel, and 0.79 m² of shuttering.
Essential Checklist+−
Complete these critical checks before approving the work or proceeding to the next construction stage.
✓Opening & Bearing Verification+-
- Opening span used matches the actual door/window frame size shown on the architectural drawing, not an assumed round number.
- Bearing length on each side is confirmed against the applicable structural code or engineer's note, not just this calculator's default.
- Openings placed close together (piers between them) have the pier width checked against the minimum required for bearing to actually develop on both sides.
- Any load concentrated above the opening (beam end, truss point load, AC unit bracket) is flagged to the structural engineer rather than sized using the standard rule-of-thumb.
✓Lintel Sizing & Concrete+-
- Lintel depth and width used are taken from the structural drawing, or confirmed adequate for the span and load above (not just this calculator's rule-of-thumb suggestion).
✓Reinforcement Verification+-
- Main bar diameter and count match the structural drawing, placed near the bottom with correct concrete cover.
- Stirrup diameter and spacing match the drawing, with closed loops properly hooked and tied.
- Main bars extend the full required development/anchorage length into the bearing wall on each side, not cut short at the opening edge.
✓Casting & Curing+-
- Lintel is cured (kept moist) for the applicable minimum period before formwork is struck or loaded.
- Formwork is not removed, and no load is placed on the lintel, before the concrete has reached adequate strength.
- Concrete is properly compacted/vibrated around the closely spaced reinforcement without segregating the mix, given the lintel's typically shallow depth.
✓Final Check+-
- Door/window frame fixing points and any embedded fixtures clear the lintel's reinforcement cage rather than drilling through a main bar or stirrup later.
Full QC Checklist+−
Verification checklist for RCC lintels — covering opening/bearing verification, sizing, reinforcement, casting/curing, and final check. Use the Essential Checklist for critical checks; expand to Full QC Checklist for complete quality assurance.
✓Opening & Bearing Verification+-
- Opening span used matches the actual door/window frame size shown on the architectural drawing, not an assumed round number.
- Bearing length on each side is confirmed against the applicable structural code or engineer's note, not just this calculator's default.
- Wall on both sides of the opening is solid masonry (not another opening or a control joint) for the full bearing length.
- Openings placed close together (piers between them) have the pier width checked against the minimum required for bearing to actually develop on both sides.
- Lintel level is consistent across openings on the same wall line, unless a step is specifically shown on the drawing.
- Any load concentrated above the opening (beam end, truss point load, AC unit bracket) is flagged to the structural engineer rather than sized using the standard rule-of-thumb.
✓Lintel Sizing & Concrete+-
- Lintel depth and width used are taken from the structural drawing, or confirmed adequate for the span and load above (not just this calculator's rule-of-thumb suggestion).
- Concrete mix ratio/grade matches the project specification for the exposure condition.
- Formwork (shuttering) is level, properly supported, and leak-proof at joints before pouring.
- Lintel width matches the wall thickness it sits in, with no unintended step or overhang at either face.
- Sunshade, chajja, or drop-wall projections cast integrally with the lintel are confirmed on the drawing before formwork is built, since they change the pour sequence and reinforcement.
- Aggregate size used in the mix suits the lintel's minimum dimension and reinforcement spacing, so aggregate doesn't bridge and leave voids.
✓Reinforcement Verification+-
- Main bar diameter and count match the structural drawing, placed near the bottom with correct concrete cover.
- Top (hanger) bars are included and properly tied to the stirrup cage, not omitted as a shortcut.
- Stirrup diameter and spacing match the drawing, with closed loops properly hooked and tied.
- Main bars extend the full required development/anchorage length into the bearing wall on each side, not cut short at the opening edge.
- Cover blocks are placed on all faces (bottom, sides, and top) to hold the cage centered in the formwork during the pour, not just resting on the shutter base.
- Where two lintels meet at a corner or T-junction, main bars are lapped or continued per the drawing rather than simply butted together.
✓Casting & Curing+-
- Concrete is poured in one continuous operation for each lintel to avoid a cold joint.
- Lintel is cured (kept moist) for the applicable minimum period before formwork is struck or loaded.
- Formwork is not removed, and no load is placed on the lintel, before the concrete has reached adequate strength.
- Concrete is properly compacted/vibrated around the closely spaced reinforcement without segregating the mix, given the lintel's typically shallow depth.
- Props supporting the lintel formwork are not disturbed or removed early by other trades working nearby before the minimum curing period is complete.
- Curing method (ponding, wet hessian, or curing compound) suits the site conditions and ambient temperature, particularly in hot or windy weather.
✓Final Check+-
- Lintel is level and both bearings are visibly resting on solid wall after formwork removal.
- No visible honeycombing, cracking, or exposed reinforcement on the finished lintel surface.
- Total concrete and steel used is reconciled against this calculator's estimate before closing out the item in records.
- Door/window frame fixing points and any embedded fixtures clear the lintel's reinforcement cage rather than drilling through a main bar or stirrup later.
- Any minor surface defects are patched with a compatible repair mortar and cured before plastering starts, not concealed under plaster alone.
- Lintel is photographed and recorded before it's covered by masonry above and plaster on both faces, for future reference.
Reference Tables
Typical bearing length by opening span
| Opening Span | Commonly Cited Minimum Bearing (each side) |
|---|---|
| Up to 1.2 m | 100-150 mm |
| 1.2 m - 1.8 m | 150 mm |
| 1.8 m - 2.4 m | 200 mm |
| Above 2.4 m | 200-230 mm, confirm with structural design |
Rule-of-thumb lintel depth by span
| Opening Span | Depth (span ÷ 10 to span ÷ 12) | Practical Minimum |
|---|---|---|
| 0.9 m | 75-90 mm | 150 mm |
| 1.2 m | 100-120 mm | 150 mm |
| 1.8 m | 150-180 mm | 150-180 mm |
| 2.4 m | 200-240 mm | 200-240 mm |
Standard bar diameters and unit weight
| Diameter (mm) | Unit Weight (kg/m) |
|---|---|
| 8 mm | 0.395 |
| 10 mm | 0.617 |
| 12 mm | 0.889 |
| 16 mm | 1.580 |
| 20 mm | 2.469 |
These are commonly referenced conventions, not a universal standard — always confirm bearing length, lintel depth, and reinforcement against your project's applicable structural code before finalizing.
Usage Guide
- Use during early estimation to size lintel concrete, steel, and shuttering across all door/window openings on a floor plan.
- Enter the actual opening span from the architectural drawing, not a rounded assumption.
- Group identical openings using the "Number of Openings" field rather than re-entering the same dimensions repeatedly.
- Cross-check the reinforcement and lintel size against the structural drawing before ordering steel or pouring concrete.
- Download the checklist PDF alongside the estimate for a site-ready verification record.
Practical Lintel Tips
- Keep the same lintel depth across all openings on one wall/floor where practical — it simplifies formwork and keeps the top of openings level.
- Never reduce bearing length to fit a tight opening spacing — reduce the lintel depth or consult a structural engineer instead.
- Cast the lintel in one continuous pour; a cold joint partway through significantly weakens it.
- Keep the top of the lintel level with (or above) the point where the next masonry course starts, so brick/block coursing stays consistent.
- Don't strike the shuttering or load the lintel until it has cured for the applicable minimum period — a lintel loaded too early is a common cause of mid-span cracking.
Common Mistakes
- Using the opening width as the lintel length, forgetting the bearing length needed on each side.
- Skipping stirrups or top hanger bars on the assumption that a lintel is "too small to need them."
- Reducing bearing length below the applicable minimum to squeeze in a wider opening.
- Not accounting for extra load on the lintel from a beam, slab, or another opening directly above it.
- Removing formwork or loading the lintel before adequate curing time has passed.
Limitations
- Estimates material quantity for one RCC lintel over a single opening only — does not model combined lintels spanning multiple openings or lintel-cum-sunshade designs.
- Does not perform structural design (load calculation, bending/shear/deflection checks) — lintel size and reinforcement must come from an approved structural drawing for anything beyond routine, lightly loaded openings.
- Does not model lap splices — lintels are almost always shorter than a standard 12 m stock bar length, so laps are rarely needed; if yours is unusually long, account for laps manually.
- Bearing length and depth rules of thumb are commonly cited conventions, not a single universal structural code requirement.
- Cost excludes labour, transport, and wastage/offcuts beyond the calculated quantities.
Related Construction Calculators
You may also find these calculators useful for openings and RCC work:
- Beam Steel Calculator
Estimate main bar and stirrup quantities for a full beam.
- Concrete Beam Calculator
Estimate concrete volume for a full RCC beam.
- Shuttering Calculator
Detailed formwork planning for beams, columns, and slabs.
- Bar Bending Schedule Calculator
Build a full multi-bar-mark schedule across a job.
- Wall Masonry Calculator
Estimate brick/block quantity for the surrounding wall.
- Rebar Weight Calculator
Quick single-bar weight lookup by diameter and length.
Disclaimer: This calculator provides approximate results for planning and estimation purposes only. Actual requirements may vary based on site conditions, materials, workmanship, and local building regulations. Always consult a qualified engineer, architect, or construction professional before making final decisions.