Calculate plasterboard sheets, screws, and tape for a ceiling
Plasterboarding a ceiling is one of the most common tasks in UK home renovation and new-build projects. Whether you are replacing a damaged ceiling, lining a loft conversion, or finishing a new extension, this calculator helps you work out exactly how many sheets of plasterboard you need, along with the screws and jointing tape required to complete the job. Ceiling plasterboard installation differs from wall boarding in several important ways: the boards must be supported against gravity, the joist spacing determines the maximum unsupported span (and therefore the board width), and the fixings must be strong enough to hold the board in place permanently. This calculator accounts for joist spacing by adjusting the sheet size -- standard 1200mm-wide sheets for 600mm centres, and narrower 900mm sheets for 400mm centres. The calculator also estimates the number of drywall screws and metres of jointing tape needed, helping you create a complete shopping list in one step. Board thickness options (9.5mm, 12.5mm, and 15mm) are provided for reference, though the sheet area calculation remains the same regardless of thickness.
To calculate plasterboard for a ceiling: 1. Measure and enter the ceiling length in metres. Measure the longest dimension of the room. 2. Measure and enter the ceiling width in metres. Measure the shortest dimension. 3. Select the joist spacing. Check your ceiling joists -- they will typically be at either 400mm or 600mm centres. This affects which sheet size to use. 4. Select the board thickness. The default 12.5mm is standard for most domestic ceilings. Use 9.5mm as a lightweight option or overlay. Use 15mm for enhanced fire resistance or sound insulation. 5. Adjust the waste allowance. The default 10% is suitable for rectangular rooms. Increase to 15% for L-shaped rooms, rooms with many downlights, or awkward angles. 6. Review the results showing ceiling area, sheet count (with waste), screw quantity, and jointing tape length. Screws are typically sold in boxes of 200, and tape in 30m or 50m rolls.
The plasterboard ceiling calculation is straightforward: Ceiling Area = Length x Width For 600mm joist centres, the standard sheet is 2400x1200mm = 2.88 m2. For 400mm joist centres, the narrower sheet is 2400x900mm = 2.16 m2. Sheets Needed = ceiling(Ceiling Area / Sheet Area) Sheets with Waste = ceiling(Sheets Needed x (1 + Waste % / 100)) For a 5m x 4m ceiling with 600mm spacing: area = 20 m2, sheets = ceiling(20 / 2.88) = 7, with 10% waste = ceiling(7 x 1.1) = 8. Screws = ceiling(Ceiling Area x 24) -- approximately 24 screws per square metre, based on 150mm screw spacing along joist lines at 600mm centres. Jointing Tape = ceiling(Ceiling Area x 1.5) -- approximately 1.5 metres of tape per square metre of ceiling, covering all board-to-board joints and perimeter joints. The chart shows sheets needed alongside screw boxes (boxes of 200) and tape rolls (30-metre rolls) for easy purchasing reference.
When plasterboarding a ceiling, always use a board lifter or extra pairs of hands -- ceiling boards are heavy and unwieldy. Fix boards perpendicular to the joists for maximum strength. Stagger the end joints so they do not line up across adjacent boards. Use 38mm drywall screws for 12.5mm board (or 32mm for 9.5mm board) driven into the joist centres. For fire-rated ceilings between floors, check Approved Document B of the Building Regulations for the required board specification. In a loft conversion, the ceiling may also need to meet thermal requirements per Approved Document L, in which case insulation must be fitted above or between the joists before boarding. All plasterboard should comply with BS EN 520 and carry appropriate CE marking.