Lintel Sizing Calculator — What Size Lintel Do I Need?

This calculator determines the minimum lintel length by adding the required bearing length to each side of the opening width. It then provides guidance on suitable lintel types based on your wall construction and loading conditions.

The formula

Minimum lintel length = Opening width + (Bearing × 2)

For example, a 1200mm opening with 150mm bearing each side needs a lintel at least 1500mm long. We then recommend the nearest standard manufactured length.

Lintel type guidance

Our recommendations reference common UK lintel ranges from manufacturers such as Catnic and IG Lintels. The correct lintel depends on:

• Wall type (single leaf, cavity, or solid)
• Load condition (roof only, floor + roof, multi-storey)
• Opening width (wider = heavier duty lintel)
• Cavity width (for cavity wall lintels)

Important disclaimer

This calculator provides general guidance only. Lintel selection for structural openings must be confirmed by a structural engineer and approved by Building Control under the Building Regulations (Approved Document A). This is particularly important for load-bearing walls, wide openings, and multi-storey buildings.