Lintel Size Calculator
Enter the width of the opening, the wall type and what the lintel carries. The calculator gives the lintel length to buy, the bearing at each end and a guide to the concrete lintel depth.
- Length with bearings
- Standard lengths
- Depth by span
Measure the opening from brick to brick, not the frame.
A lintel bridges the gap over a door or window. It must rest on solid wall at each end, at least 150 mm for most openings. So a 900 mm doorway needs a lintel at least 1,200 mm long.
Lintel size chart
150 mm bearings. Search for an opening.
| Opening (mm) | Lintel length (mm) | Concrete depth, light (mm) | Concrete depth, loaded (mm) |
|---|---|---|---|
| 600 | 900 | 65 | 100 |
| 900 | 1200 | 65 | 100 |
| 1200 | 1500 | 65 | 100 |
| 1500 | 1800 | 100 | 140 |
| 1800 | 2100 | 100 | 140 |
| 2400 | 2700 | 140 | 215 |
| 3000 | 3300 | 215 | 215 |
Concrete depths are a guide. Check the maker's load table.
Opening and lintel
Wall and a floor above. Slide the opening.
The lintel is the bar across the top, resting on the wall at each side.
How to size a lintel
Opening plus bearings. Step through it.
Measure
Brick to brick.
Steel lintels are sized by the maker for the wall type and load. Choose from their table using the opening and load.
Concrete, steel or timber
Lintel types. Compare them.
Precast and reinforced.
Pressed or box section.
Doubled joists.
In cavity walls, steel cavity lintels include insulation and a damp tray to stop cold bridging and leaks.
Before fitting
Lintel checks. Tick each item.
Tick each item as you go.
Wider openings or point loads from beams need an engineer's calculation.
What you get
Lintel size. Each tile explains one result.
To buy.
Each end.
Concrete guide.
For the wall.
What it carries.
Steel lintels come in 150 mm steps, so round up to the next one.
Frequently Asked Questions
No question matches that search.
How long should a lintel be?
The opening width plus at least 150 mm at each end.
What size lintel for a standard door?
A doorway of about 900 mm needs a lintel at least 1,200 mm long.
How much bearing does a lintel need?
At least 150 mm each end, and more for wide openings or heavy loads.
Can I use a concrete lintel in a cavity wall?
Usually only for the inner leaf. Steel cavity lintels are normally used for the whole wall.
Do I need building control for a new opening?
Yes, for most new or widened openings in a loadbearing wall.
What is the difference between a lintel and a beam?
A lintel spans a door or window. A beam carries a floor or wall over a larger span.
How deep should a lintel be?
It depends on span and load, from about 65 mm for a short light lintel to 215 mm or more.
Bridge the opening safely
Take the opening, add proper bearing at each end and round up to a stock length. Then choose the type and depth for the wall and the load above it.
More size calculators
Each one has its own calculator, worked examples and answers to common questions.