Paint Calculator

Formula & Calculation Methodology

Net Wall Area (sq ft) = (2 × (Length + Width) × Height) − Openings | Paint Litres = (Net Wall Area × Coats) / Coverage Rate per Litre

	ext{Area} = 2(L + W)H - 	ext{Openings}, quad 	ext{Litres} = rac{	ext{Area} 	imes 	ext{Coats}}{	ext{Coverage}}

Step-by-Step Worked Example

Room: 12 ft Length × 15 ft Width × 10 ft Height | 1 Door & 2 Windows | 2 Coats Emulsion (100 sq ft/L coverage)

1. Gross Wall Area = 2 × (12 + 15) × 10 = 540 sq ft
2. Deduct Openings: 1 door (21 sq ft) + 2 windows (32 sq ft) = 53 sq ft
3. Net Surface Area = 540 − 53 = 487 sq ft
4. Total Area for 2 Coats = 487 × 2 = 974 sq ft
5. Paint Litres Required = 974 / 100 = 9.74 Litres (approx 10 Litres)

How Paint Quantity is Estimated

Estimating wall paint quantity for house interiors or exteriors in India involves measuring total wall surface area, deducting non-paintable openings (doors and windows), multiplying by the required number of paint coats, and dividing by the paint coverage rate.

Wall Area Measurement

Gross Wall Area = 2 × (Room Length + Room Width) × Ceiling Height

Doors and Windows Deductions

• Standard Single Door = 21 sq ft (3 ft × 7 ft)
• Standard Window = 16 sq ft (4 ft × 4 ft)

Number of Coats

A minimum of 2 coats of emulsion paint is recommended for new walls or color changes to ensure even finish and opacity.

Coverage Rates in India

1 Litre of standard Indian interior emulsion paint covers approximately 120 to 140 sq ft for 1 coat (or 60 to 70 sq ft for 2 coats).

Paint Calculation Example

For a 12x15 ft room with 10 ft height (487 sq ft net wall area, 2 coats, 100 sq ft/L coverage):

Paint Required = (487 × 2) / 100 = 9.74 Litres (Buy 10 Litres bucket).

Wastage and Primer

Add 10% extra paint for roller wastage, touching up, and future maintenance.

Frequently Asked Questions