Lintel Load and Moment Calculator
Wall load above the opening, moment and steel estimate.
With the default inputs: Clear span 1.5 · Wall thickness 240 · Masonry density 19 kN/m³ etc.Mid-span moment 0.98 kN·m
Edit the inputs below to recalculate.Inputs
Result
| Effective wall height | 0.50m |
| Wall line load | 2.28kN/m |
| Self weight | 1.20kN/m |
| Total line load | 3.48kN/m |
| Support shear | 2.61kN |
| Effective depth h0 | 165mm |
| Estimated steel area | 18mm² |
| Bars (Φ12 / Φ14) | 0.2 / 0.1bars |
A lintel in masonry only carries the wall weight within a limited height - the masonry above arches over to the sides, so codes allow min(actual height, span/3) with a 45° spread. The moment uses a simply supported beam, ql²/8, with at least 240 mm bearing each end (and no less than the wall thickness). The steel area from M/(0.9·fy·h0) is a rough estimate that ignores the real compression block and minimum ratios - for scheme checks only. Formal design should use a precast lintel catalogue or a proper concrete calculation, and must consider any concentrated loads above.
Reverse: known result, work out one input
Enter a target result; the other inputs stay fixed and this one is worked out.
Formula
| Effective height = min(actual, span/3) | 45° spread |
| q = thickness × effective height × density + self weight | kN/m |
| M = q·l²/8, V = q·l/2 | simply supported |
| As ≈ M / (0.9·fy·h0) | rough estimate |
How to work it out
- Establish the wall height carried by the lintel: by 45° dispersion, take a third of the clear span or the actual height, whichever is less — only a triangular wedge above the opening is carried.
- Line load q = wall height × thickness × masonry unit weight (kN/m), plus 1.0-1.5 kN/m² for plaster and finishes.
- Moment M = q × L² ÷ 8 for a simply supported span L.
- Steel area As ≈ M ÷ (0.9 × h₀ × fy) with h₀ = depth − cover − d/2. This is a rough check; formal design follows the concrete code.
- Check shear too: V = q × L ÷ 2, adding stirrups or depth where capacity is short.
Where it goes wrong
- Taking the full wall height above the opening — 45° dispersion means the masonry arches over, so only the triangle is carried; the full height overstates load two to threefold and over-reinforces the lintel.
- Ignoring plaster and finishes — 40 mm both sides is about 0.8 kN/m², which is 15% of the load on a 1.5 m span.
- Mixing conventions between moment and reinforcement — use the clear span for moment and the effective depth for steel consistently, and check shear within the bearing length.
Material and cost
Precast lintels run 60-120 each by span (about 90 for 1.5 m); cast in situ costs 450 per m³ of concrete plus steel and formwork, roughly 120-180 per metre. Precast is quicker but fixed in size; in-situ is flexible but needs formwork.
On site
- Bearing length is at least 250 mm, or 300 mm in seismic work; add a concrete pad where masonry strength at the bearing is inadequate.
- Above 1.5 m clear span, or with concentrated loads, standard precast lintels do not apply — design and cast in situ.
- Where a lintel coincides with a ring beam, measure it as the ring beam and do not count both.
Basis
- GB 50003-2011 Code for design of masonry structures, Section 7.2 (lintels)
- GB 50011-2010 Code for seismic design of buildings, Section 7.3
- GB 50203-2011 Code for acceptance of masonry construction, Chapter 8
FAQ
Why count only 0.5 m of a 3 m wall?
How much bearing does a lintel need?
If the calculated steel is tiny, can it be omitted?
Cite this page
Use this format in reports, method statements or coursework. The link is permanent.
Building Calculator. Lintel Load and Moment Calculator. 2026-10-25. https://jianzhujisuan.com/en/lintel-load