🎨 Paint Quantity Estimator

How to Calculate Interior Wall Paint Requirements for Australian Homes

Tackling a room refresh with a fresh coat of low-sheen acrylic or washable interior paint is one of the most rewarding home improvement jobs. However, standing in front of the retail trade rows at your local paint outlet or Bunnings trade center trying to select between 1L, 2L, 4L, or massive 10L drums can be intimidating. Buying too little paint means running out mid-wall, risking an uneven finish when you apply a fresh batch, while purchasing excessive volumes leaves expensive product drying out permanently in your garage storage.

Understanding Paint Coverage and Spreading Rates

In Australia, the standard coverage metric for top-tier architectural wall paint (such as Dulux, Taubmans, or Wattyl premium lines) is mathematically rated at **16 square metres ($m^2$) per Litre per single coat**. This coverage rate can drop down to roughly 12m² to 14m² per Litre if you are applying paint directly over raw, unprimed plasterboard sheets or highly porous masonry block work, which drinks liquid rapidly. For previously colored or sealed internal walls, planning your layout around the 16m²/L benchmark ensures a highly accurate material budget.

Subtracting Openings for High Precision

To get a genuinely precise evaluation, you cannot simply calculate raw wall dimensions ($Length \times Height$). You must strip out layout voids where paint will never be applied. A standard Australian interior passage door averages roughly **2 square metres** of surface footprint ($2.04m \times 0.82m$), while standard bedroom sliding windows account for approximately **1.5 to 2 square metres** of space. Taking the time to filter these out prevents buying unneeded liquid volume. Always budget for a minimum of **two distinct coats** for standard interior repaints to establish complete color saturation, blocking power, and durable washability profiles.