Ceiling Grid Calculator — Runners, Tees, Wires & Tiles

Main runners are spaced at 1200mm centres for both 600×600mm and 600×1200mm tile modules. The runners usually run along the length of the room. They are suspended from the structural ceiling/soffit above using drop wires or adjustable hangers at maximum 1200mm centres along each runner.

Main runners are the primary load-bearing members running the full length of the room at 1200mm centres. Cross tees are shorter sections that slot into the main runners at right angles to form the grid. The 1200mm cross tees connect between adjacent main runners and sit at 600mm centres along the length for both tile modules. For 600×600 tiles, an extra 600mm cross tee bisects each 1200×600mm bay; for 600×1200 tiles the 1200mm cross tees are still at 600mm centres but the 600mm secondary tees are dropped, so the same number of 1200mm tees but no 600mm tees.

Suspension wires (or adjustable hangers) should be at maximum 1200mm centres along each main runner, with the first wire no more than 450mm from each wall (BS EN 13964). For a 4m × 3m room (main runners running along the 4m length), there are 4 runner rows (3000 ÷ 1200 + 1) and 5 wire positions per runner (4000 ÷ 1200 + 1), giving roughly 20 suspension wires. Each wire must be securely fixed to the structural soffit above using appropriate fixings.

Wall angle (also called perimeter trim or L-trim) is an L-shaped metal trim fixed around the entire perimeter of the room at the desired ceiling height. It supports the grid edge tiles and provides a neat finish where the ceiling meets the walls. It comes in 3m lengths and is fixed to the wall at approximately 450mm centres using screws and rawlplugs.

Run it once for each rectangular section and add the main runner, cross tee, suspension wire and tile counts. Those quantities follow the ceiling area and grid layout, so entering the overall bounding dimensions instead would over-order them by the area of the missing notch. Allow a few spare tiles on top: the real grid runs continuously through the join between sections, so its alignment in the second section can add some extra edge cuts. The wall angle is the one figure you should not add up from the section runs, because the join line between sections is not a wall and summing section perimeters counts it twice. Use an exact shortcut instead: for a room shaped like a rectangle with a corner cut off, the true perimeter is exactly 2 × (overall length + overall width) of the bounding rectangle, because the notch walls line up with the wall sections they replace. Divide that by 3m and round up for the wall angle lengths.

600×600mm tiles are the most common in the UK and are easier to handle (lighter, less likely to sag). 600×1200mm tiles are more common in commercial settings and create fewer grid lines for a cleaner look. Both modules use 1200mm main runner spacing and 1200mm cross tees at 600mm centres. The 600×600 layout adds 600mm secondary cross tees to subdivide each 1200×600mm bay into two squares; the 600×1200 layout drops those 600mm tees (the 1200mm tile side spans the full bay), which is why it has fewer grid lines and fewer components. Choose based on visual preference and tile availability.