2026-11-08T09:20:59

Calculate Wall Paint Quantity from Coverage, Coats and Reserve

To calculate wall paint quantity in a way you can check, measure the net area (height times width, minus doors and windows), multiply by the number of coats, then divide by the official coverage on the can or technical data sheet—units may be m² per kilogram or m² per litre, and they are not interchangeable. That theoretical figure still excludes rough walls and site leftovers: Avian’s guide adds about 10–15 percent for rough, cracked or never-painted surfaces, plus a 5–10 percent reserve for small repairs. This article joins Dulux’s formula with Avitex, Vinilex, Pentalite and Catylac Interior coverage figures verified today; it is not a price-per-square-metre table.

Key Facts

Dulux: measure height and width, subtract windows and doors; decide how many coats; divide by coverage (m²/L) on the pack or website. Example: 20 m perimeter (4×6 m room) × 2.5 m height = 50 m²; two coats means paint for 100 m² (2026-11-08, source: Dulux Indonesia: how to calculate how much paint you need).
Avitex wall paint TDS (effective 1 Jan 2020): theoretical spreading rate 10–12 m²/kg per coat, depending on porosity, film thickness and substrate; 2 coats recommended; dry film about 60 microns, wet 100–120 microns; system 1× alkali primer + 2× Avitex (2026-11-08, source: Avian Brands: Avitex wall paint TDS (effective 1 Jan 2020, TDS/MP/0220)).
Nippon Vinilex TDS: theoretical spreading rate 10–12 m²/litre/coat; the product page states 9–12 m²/litre/coat (6–8 m²/kg/coat). Two official figures, not identical—use the one on the lot you buy (2026-11-08, source: Nippon Paint Indonesia: Vinilex TDS).
Dulux Pentalite: coverage 12–14 m²/L, two coats, matt finish; the product-page calculator is based on two coats (2026-11-08, source: Dulux Indonesia: Dulux Pentalite product page).
Avian (10 Jun 2026): as a general guide 1 litre covers about 10–12 m² per coat; rough, cracked or never-painted walls need about 10–15% more; keep a reserve of about 5–10% of the calculated total for corrections and touch-up (2026-11-08, source: Avian Brands: exterior wall paint quantity guide (10 Jun 2026)).

The manufacturer formula to calculate wall paint quantity

Dulux sets out three steps. First, measure the height and width of each surface, multiply to get square metres, then subtract windows and doors. Second, decide how many coats you need. Third, divide the first result by the spreading rate in square metres per litre printed on the pack or the product website. In the calculator-formula example, a room 4 metres wide and 6 metres long is totalled as a 20-metre perimeter, times 2.5 metres high equals 50 square metres; two coats means you need enough paint to cover 100 square metres—then divide that number by the chosen product’s coverage. Remember to subtract doors and windows from the 50 square metres when they exist.

Read the coverage unit: m²/kg is not automatically m²/L

The costliest mistake is treating kilograms as litres. The Avitex TDS (effective 1 January 2020) states a theoretical spreading rate of 10–12 m²/kg per coat and packs of 1 kg, 5 kg and 25 kg; specific gravity is 1.40–1.60 kg/litre depending on colour, so 10 m²/kg is not 10 m²/L. Dulux Pentalite uses 12–14 m²/L, while Dulux Catylac Interior uses 10–12 m²/kg. The Nippon Vinilex TDS uses 10–12 m²/litre/coat, but the matching product page lists 9–12 m²/litre/coat or 6–8 m²/kg/coat. When you calculate wall paint quantity, copy the unit exactly as printed for the product you will buy; do not swap kg and L.

Worked numbers: 100 m² of coverage from Dulux’s example

Take Dulux’s example without door or window deductions: 50 m² of wall, two coats, equal to 100 m² of coverage. With Dulux Pentalite at 12–14 m²/L, the theoretical need is about 100÷14 to 100÷12 litres, or roughly 7.1–8.3 litres. With Avitex at 10–12 m²/kg, the theoretical need is about 100÷12 to 100÷10 kilograms, or roughly 8.3–10 kg. If you use the Vinilex product-page figure of 6–8 m²/kg, the range becomes 100÷8 to 100÷6 kilograms, or about 12.5–16.7 kg—higher because coverage per kilogram is lower. The spread shows why you must match the lot and the unit, not average brands together.

Do not guess the coat count. The Avitex TDS recommends two finish coats over one coat of Avitex Alkali Resisting Primer; the primer is a separate product with its own coverage. The Pentalite and Catylac Interior pages and the Dulux calculator start from two finish coats. If the colour change is very contrasting, both the Avian and Dulux calculators warn that extra coats may be needed—that raises the “number of coats” numerator; it does not change the formula.

Rough-wall allowance and reserve when you calculate wall paint quantity

TDS theoretical figures assume the test film thickness. Avian separately publishes two site adjustments. First, rough, cracked or never-painted surfaces usually absorb more: add about 10–15 percent. On a 10 kg theoretical Avitex example, a 15 percent addition is about 1.5 kg, taking the subtotal to 11.5 kg. Second, keep a reserve of about 5–10 percent of the total already calculated, for application mistakes, small repairs or later touch-up; 10 percent of 10 kg is 1 kg. Those figures are published ranges, not laboratory constants, and should not be merged into one undocumented “magic factor”.

Primer must be calculated on its own. The Avitex system is one alkali-primer coat on new walls after moisture of 17–19 percent and pH below 9, or after about 28 days of drying in normal weather, then two Avitex coats. Thin Avitex with at most 20 percent clean water on the first coat and 10 percent on the second—adding extra water changes film thickness and voids the coverage maths. homeX can help match an interior or exterior paint to the coverage printed on the pack before you buy, without replacing the maker’s official figures.

calculate wall paint quantity: related articles and products

FAQ

What is the basic formula to calculate wall paint quantity? Effective area (height × width, minus doors and windows) times the number of coats, then divide by official coverage. Dulux example: 50 m² × 2 coats = 100 m² of coverage, then divide 100 by the pack’s m²/L or m²/kg.

When is coverage in m²/kg and when in m²/L? Follow the TDS or product page. Avitex and Catylac Interior use m²/kg; Pentalite uses m²/L; the Vinilex TDS uses m²/litre and its product page also lists m²/kg. Do not swap units even when the numbers look similar (for example 10–12).

What reserve is reasonable beyond the theoretical figure? Avian’s 10 June 2026 guide: about 10–15% extra for rough, cracked or unpainted walls, plus a reserve of about 5–10% of the calculated total for corrections and touch-up. That does not replace reading the coverage on the lot you buy.

For building and renovation material needs, reach the homeX team on WhatsApp +62 821 1818 998, by email at homex9998@gmail.com or through our contact page.

Sources: Dulux Indonesia: how to calculate how much paint you need; Avian Brands: Avitex wall paint TDS (effective 1 Jan 2020, TDS/MP/0220); Avian Brands: exterior wall paint quantity guide (10 Jun 2026); Nippon Paint Indonesia: Vinilex TDS; Nippon Paint Indonesia: Nippon Vinilex product page; Dulux Indonesia: Dulux Pentalite product page; Dulux Indonesia: Dulux Catylac Interior product page