Ceiling tiles = full tiles plus border tiles, plus about 10% spare. A 13 × 11 ft room in 2×2 ft tiles holds 42 tiles (7 across by 6), so you buy 47, which is three cartons of 16. The grid that carries them is 3 main tees, 18 four-foot and 14 two-foot cross tees (before waste), 48 ft of wall angle and 15 hanger wires. That is the whole material list for a drop ceiling, also called a suspended ceiling or false ceiling.
How the drop ceiling layout is calculated
Armstrong's installation guide starts with balanced borders. Divide each room dimension by the panel size, split the remainder between the two walls, and if each border would be under 10 in, take one full panel out and add it to the remainder. In the default room, 13 ft is 6 panels of 2 ft and a 12 in remainder, which would give two 6 in borders. So the calculator uses 5 full panels and splits 36 in into two 18 in borders. The 11 ft width works the same way: 4 full panels and two 18 in borders. Armstrong's own example is 28 ft 9 in: 14 panels leave 9 in, so the borders become 16½ in around 13 full panels.
The grid follows from the panel size. Main tees run 48 in apart, 4 ft cross tees cross them every 24 in, and for 2×2 tiles 2 ft cross tees join the midpoints of the long ones (Armstrong 3.1.1). Main tees come in 12 ft lengths, cross tees in 4 ft and 2 ft, and wall angle in 12 ft or 10 ft lengths (USG Donn DX/DXL data sheet). The plan drawn under the result is to scale, with the border tiles shaded and the hangers marked on each main.
Full panels = ⌊room ÷ panel⌋. Border = (room − full × panel) ÷ 2, or (room − (full − 1) × panel) ÷ 2 if that is under 10 in. Tiles = cells across × cells along. Mains = a row every 48 in.
Hanger wire, wall angle and clearance
Hanger wire is 12 gauge galvanized, spaced no more than 4 ft apart along each main, and each wire wraps itself three full turns within 3 in (Armstrong 5.3 to 5.7, ASTM C636). The wire needs at least 4 in of drop from the grid to the structure, and you should leave 3 in under ducts and pipes so a tile can be tilted into the opening. The calculator counts one wire near each wall and evenly between them, and cuts each one to your drop plus a 12 in allowance for the wraps. Wall angle is fixed to the wall every 16 to 24 in, and the inside corners are mitered for a neat look.
Ceiling tile presets: Armstrong and USG
The presets carry the size and carton count printed by the maker, and you can change the count:
| Tile | Size | Per carton | Coverage |
|---|---|---|---|
| Armstrong Fine Fissured 1732 | 2×2 ft, 5/8 in | 16 | 64 sq ft |
| Armstrong Fine Fissured 1733 | 2×4 ft, 5/8 in | 10 | 80 sq ft |
| USG Radar Basic | 2×2 ft, 5/8 in | 16 | 64 sq ft |
| USG Radar | 2×4 ft, 5/8 in | 8 | 64 sq ft |
2×2 or 2×4 ceiling tiles?
A 2×4 layout needs no 2 ft cross tees, so the grid has fewer parts, but each tile is 8 sq ft and a broken one wastes twice as much. Choose 2×2 for a look with more joints and easier handling in tight rooms. For the metric grid pick a 600 × 600 mm tile: the main tees are then 1200 mm apart and the cross tees 1200 and 600 mm, and mains are sold as 3600 mm lengths. Tile counts per carton vary by maker, so set your own.
Before and after the ceiling goes up
Lights and vents decide where whole tiles are cut, so plan them with the recessed lighting calculator before you mark the grid. Add insulation above the ceiling first if the room is under an attic. Paint the walls before the wall angle goes up with the paint calculator, and if you prefer a fixed ceiling, the drywall calculator covers the board. For the room area on its own use the square footage calculator. More wall and ceiling tools are on the walls and ceilings hub.