Jointing Compound Calculator — Plasterboard Tape & Filler

This calculator estimates the jointing compound (filler) and tape required for plasterboard (drywall) installation. It uses your total area to work out the number of boards, then calculates joint lengths for both flat (board-to-board) and internal corner joints.

The 3-coat system

• Bedding coat (50mm wide): A thin layer of compound is applied along the joint and paper tape is pressed into it. Typical allowance ~0.15 kg/m.
• Filling coat (150mm wide): Once the bedding coat has set, a wider coat is applied over the tape to build up the joint level with the board face. Typical allowance ~0.35 kg/m.
• Finishing coat (250mm wide): A final thin coat is feathered out to blend the joint seamlessly into the surrounding board. Typical allowance ~0.25 kg/m.

These per-metre figures are typical trade allowances for a generic 3-coat system, not a manufacturer-published rate — actual usage varies with joint quality, board gap width and operator technique. Always cross-check the coverage on your chosen product’s data sheet (for example, Knauf Fill & Finish covers roughly 30 m² of board area per 20 kg).

Corner joints

Internal corners (where walls meet walls or walls meet ceilings) require paper tape folded along its centre crease. The calculator adds vertical corner joints (number of internal corners× ceiling height — default 4 for a rectangular room) plus the horizontal ceiling-to-wall perimeter.

Compound types

• Setting compound (powder):Mixed on site, sets chemically. More efficient coverage and faster recoat times. Brands: Gyproc EasiFill 60, Knauf Fill & Finish 60 Premium.
• Ready-mixed (tub):Pre-mixed and air-drying, convenient but higher moisture means ~10% more product needed and longer drying. Brands: Gyproc ProMix Lite, Knauf Fill & Finish (and the lighter Fill & Finish Light).
• Finishing compound: Lighter formula for the final coat only. Lower coverage rate but smoother finish. Often used over a setting compound base.