Paint Calculator

Paint Calculator

Work out how much interior or exterior paint you need, either from room dimensions or a direct wall area, with primer, wastage allowance, number of containers and a cost estimate.

Paint For:

Interior Exterior

Calculate Area By:

Room Dimensions Direct Wall Area

Room Dimensions

Room Length (m): Room Width (m): Wall Height (m): Number of Doors (0.9 × 2.1 m): Number of Windows (1.2 × 1.2 m): Other Deductions (sq.m, optional):

  Include ceiling area

Direct Wall Area

Total Wall Area to Paint (sq.m): Ceiling Area, optional (sq.m):

Paint, Primer & Coverage

Number of Coats: Paint Coverage (sq.m per litre, per coat): Wastage Allowance (%): Container Size for Count (litres): 1 L 4 L 10 L 20 L

  Apply primer (1 coat)

Primer Coverage (sq.m per litre):

Price per Litre of Paint: Price per Litre of Primer:

Leave Coats, Coverage and Wastage empty to use 2 coats, 10 sq.m/L for interior or 8 sq.m/L for exterior, and 10% wastage. Leave the price boxes empty to skip the cost estimate.

TOTAL PAINTABLE AREA

--m²

AREA (OTHER UNITS)

--ft²

TOTAL PAINT REQUIRED

--litres

PAINT WITH WASTAGE

--litres

PAINT CONTAINERS NEEDED

--tins

PRIMER REQUIRED

--litres

ESTIMATED PAINT COST

--

ESTIMATED TOTAL COST

--

Paint + primer

Note:

• Deductions: A standard door is taken as 0.9 × 2.1 m (1.89 sq.m) and a standard window as 1.2 × 1.2 m (1.44 sq.m); adjust the counts or use Other Deductions for non-standard openings.
• Coverage varies by product: 8–12 sq.m/litre per coat is typical for emulsion paints, but always check the coverage figure printed on your chosen paint tin, since texture, exterior weatherproof and enamel paints vary widely.
• Wastage: The default 10% allowance covers brush/roller loss, tray residue and touch-ups; increase it for textured or first-time surfaces.
• Primer: Exterior and new/bare masonry surfaces usually need a coat of primer before the finish coats; interior repaints on sound existing paint often skip it.

Reference Guide: Paint Quantity Estimation

1. Wall Area from Room Dimensions

Gross Wall Area = 2 × (Length + Width) × Height
Net Wall Area = Gross Wall Area − (Doors × Door Area) − (Windows × Window Area) − Other Deductions
Ceiling Area (if included) = Length × Width

2. Paint Volume

Paint Required (litres) = Total Paintable Area × Number of Coats / Coverage per Coat
Paint to Order (litres) = Paint Required × (1 + Wastage % / 100)
Containers Needed = Round Up (Paint to Order / Container Size)

3. Typical Coverage Rates

Surface / Paint Type	Typical Coverage per Coat
Interior emulsion, smooth wall	10 – 12 sq.m / litre
Interior emulsion, textured wall	6 – 8 sq.m / litre
Exterior weatherproof emulsion	7 – 9 sq.m / litre
Primer / sealer, wall	10 – 13 sq.m / litre
Enamel / gloss, wood or metal	12 – 15 sq.m / litre

Two finish coats are standard for a durable, even colour on a new or repainted surface; a single coat is sometimes used for minor touch-ups or when repainting in nearly the same colour.