Lintel Size Calculator

Calculator Inputs

Opening Width (mm)

Wall Thickness (mm)

Bearing Each Side (mm)

Wall Height Above Opening (m)

Opening Height (m)

Masonry Density (kN/m³)

Superimposed Load (kPa)

Tributary Width for Surcharge (m)

Load Factor

Lintel Material

Support Condition

Example Data Table

Opening Width (mm)	Wall Thickness (mm)	Height Above (m)	Material	Suggested Lintel Size (mm)
900	230	0.9	RCC M20 / Fe415	230 × 150
1200	230	1.2	RCC M25 / Fe500	230 × 200
1500	230	1.5	Precast Concrete	230 × 230
1800	300	1.8	Mild Steel	300 × 200 equivalent section

These example sizes are for quick comparison only. Final member design must follow local codes, actual loads, detailing rules, and engineer review.

Formula Used

1) Effective span: Effective Span = Opening Width + One End Bearing

2) Supported masonry height: Supported Height = minimum of wall height above opening and half of the clear span

3) Masonry line load: w_m = Density × Wall Thickness × Supported Height

4) Surcharge line load: w_s = Surcharge × Tributary Width

5) Factored load: w = (w_m + w_s + self weight) × Load Factor

6) Maximum moment: M = wL²/8 for simply supported lintels, or wL²/12 for approximate fixed ends

7) Maximum shear: V = wL/2

8) Required depth from bending: d = √(6M / f_bb)

This calculator uses a practical preliminary sizing method. It is ideal for early planning, not final structural certification.

How to Use This Calculator

Enter the clear opening width in millimeters.
Input the wall thickness and intended end bearing.
Provide the wall height above the opening.
Select masonry density and any surcharge load.
Choose tributary width for roof or floor effects.
Select the lintel material and support condition.
Click Calculate Lintel Size.
Review recommended dimensions, stress checks, and graph.
Download the results as CSV or PDF if needed.

Important: Use these results for preliminary estimating and comparison. Final construction drawings should be checked by a qualified structural engineer and matched to your local design code.

FAQs

1. What is a lintel in construction?

A lintel is a horizontal structural member placed above a door, window, or opening. It transfers wall and surcharge loads safely to the supports on both sides.

2. How do I choose the right lintel depth?

Depth depends on span, supported wall height, material strength, bearing length, and surcharge loads. This calculator estimates a practical depth using bending and load checks.

3. Why is wall thickness important for lintel sizing?

Wall thickness directly affects load on the lintel and often controls the minimum practical member width. Thicker walls usually need wider lintels and can increase total load.

4. Can I use this calculator for reinforced concrete lintels?

Yes. It includes reinforced concrete options and gives a reinforcement suggestion. Still, final reinforcement design should be reviewed using the governing structural code and actual detailing requirements.

5. Does the calculator include roof or floor loads?

Yes. You can add a superimposed load in kPa and a tributary width. That allows a quick estimate of roof or floor contribution over the opening.

6. What bearing length should I use?

Common practical bearing values start around 150 mm, but actual requirements vary by material, load, wall strength, and code. Larger loads often need larger bearings.

7. Is this calculator suitable for final structural approval?

No. It is a preliminary sizing tool. Final approval should consider code factors, crack control, reinforcement anchorage, deflection limits, fire exposure, and site conditions.

8. When should I increase the suggested lintel size?

Increase size when bending fails, bearing stress is high, spans are long, wall loads are heavy, or when future loading uncertainty suggests a stiffer and stronger member.