How do I calculate how much paint I need for a room in Sri Lanka?

Measure the wall area — perimeter × height, so 2 × (length + width) × height for a rectangular room. Subtract the doors and windows, multiply by the number of coats, then divide by the paint's spreading rate (m²/L). Add about 10% for wastage. This tool does all of that and then converts the litres into 20 L, 4 L, and 1 L tins.

How many square metres does 1 litre of emulsion paint cover?

Interior emulsion covers roughly 13 m² per litre for one coat on a smooth, previously painted wall. Exterior weathershield covers less, around 9 m²/L, because the film is thicker; enamel gloss is about 14 m²/L. The exact figure is printed on your tin's technical data sheet — enter it for the most accurate result.

How many litres of paint are in a bucket in Sri Lanka?

A full paint bucket sold at Sri Lankan hardware shops is 20 litres. Paint also comes in 4 litre and 1 litre tins. This calculator packs your requirement into the least-leftover mix of those three sizes, and also shows the fewest-tin option if you'd rather carry fewer containers.

How many coats of paint do walls need?

Two coats is the standard for a durable, even finish, and it is the convention the CIDA Building Schedule of Rates uses for its material norms. One coat is usually enough only when repainting the same colour over sound old paint. Bold or dark colours over a light base can need three. The tool lets you pick 1 to 5 coats.

Do I need primer before emulsion paint?

Bare plaster, new walls, patched areas, and previously distempered surfaces need a primer or sealer coat first so the emulsion bonds and colours evenly. Repainting over sound existing emulsion usually does not. Tick the primer option and the tool adds a one-coat primer line at 10 m²/L.

How much extra paint should I add for wastage?

A 10% wastage margin is the default here and covers roller and brush absorption, spillage, and touch-ups. CIDA and manufacturer guidance is typically 5–15%. Rough, textured, or very porous surfaces soak up more, so raise the margin toward 15% for those.

Does this calculator include the ceiling?

In Room-dimensions mode there is an "Include ceiling" toggle that adds length × width to the paintable area. Leave it off if you're only painting walls. In Wall-area mode you type the total area yourself, so add the ceiling into that figure if you want it.

What area does the tool subtract for doors and windows?

By default it deducts 1.89 m² per door (a 2.1 × 0.9 m single-leaf door) and 1.44 m² per window (1.2 × 1.2 m). If your openings are a different size, switch to "Type exact area" and enter the total opening area in square metres — that overrides the door/window count.

Does the calculator give the price of paint in rupees?

No. Prices change by brand, finish, and shop, and no single figure is authoritative, so the tool outputs litres and tins only. Take the tin list to your hardware shop for a current quote. Buying by the exact tin mix avoids both a wasted 20 L bucket and a second trip for one more tin.

Sri Lanka · Utility

Sri Lanka Paint Calculator — how much paint do I need?

Enter a room's size or a wall area and get the exact litres of paint and the 20 L / 4 L / 1 L tins to buy. It subtracts doors and windows, adds a wastage margin, and uses CIDA and manufacturer spreading rates. No signup, sources cited below.

By Induwara Ashinsana— Executive Director, Ryzera TechnologiesUpdated Jul 11, 2026

How much paint do I need?

Verified two ways

Length (m)

Width (m)

Wall height (m)

Room presets

Openings to subtract

Doors

1.89 m² each (2.1 × 0.9 m)

Windows

1.44 m² each (1.2 × 1.2 m)

Paint type

Spreading rate (m²/L per coat)

From your tin's data sheet

Number of coats

Wastage margin (%)

Roller absorption, spills, touch-ups

Net paintable area

40.23 m²

Paint per coat

3.09 L

Total paint needed

6.81 L

All coats + wastage

Least-leftover buy

1 × 4 L + 3 × 1 L

0.19 L spare

Buying option	Tins	Total	Spare
Least leftoverLeast wasted paint	1 × 4 L + 3 × 1 L	7 L	0.19 L
Fewest tinsFewest to carry	1 × 20 L	20 L	13.19 L

Same job, different paint

Paint type	Rate	Total paint	Least-leftover tins
Interior emulsion	13 m²/L	6.81 L	1 × 4 L + 3 × 1 L
Exterior weathershield	9 m²/L	9.83 L	2 × 4 L + 2 × 1 L
Enamel / gloss	14 m²/L	6.32 L	1 × 4 L + 3 × 1 L
Primer / undercoat	10 m²/L	8.85 L	2 × 4 L + 1 × 1 L

Default spreading rates follow the CIDA Building Schedule of Rates two-coat convention and published Multilac / Nippon / Dulux Sri Lanka data sheets. Litres are cross-checked against the CIDA per-100 m² norm. Override the rate with the exact figure on your tin for the most accurate result. Full sources are cited below the calculator.

How it works

The calculator uses standard perimeter-wall geometry and the paint material norms published in the CIDA Building Schedule of Rates and on manufacturer technical data sheets. Every figure comes only from your inputs and the spreading rate you choose — there is no hidden estimation model.

Gross area. In Room mode the wall area is 2 × (length + width) × height. Ticking “Include ceiling” adds length × width. In Wall-area mode you enter the area directly.
Openings. The tool subtracts 1.89 m² per door (2.1 × 0.9 m) and 1.44 m² per window (1.2 × 1.2 m), or an exact openings area if you type one. Net area is the gross minus openings, floored at zero.
Litres before wastage. (net area × coats) ÷ spreading rate. The spreading rate is the manufacturer's m²-per-litre-per-coat figure. Two coats is the CIDA convention and the default here.
Wastage. litres × (1 + wastage%). The default 10% covers roller absorption, spillage, and touch-ups; CIDA and manufacturer guidance is 5–15%.
Tins to buy. The requirement is packed into Sri Lankan tin sizes — 20 L, 4 L, and 1 L. The tool shows the least-leftover mix (rounds up to the next whole litre, fewest tins for that amount) and the fewest-tin alternative, with the spare litres for each.
Primer (optional). For a bare or new surface the tool adds a one-coat primer line at net area ÷ primer rate.

As a check, the litres are computed a second way — from the CIDA-style “litres per 100 m² for two coats” material norm, which is just 200 ÷ rate for two coats. Both methods agree to within rounding, and the calculator shows a “Verified two ways” badge when they do.

Worked examples

Bedroom, interior emulsion, two coats

Room 4 × 3.5 m, wall height 3 m, no ceiling
Gross wall area: 2 × (4 + 3.5) × 3 = 45 m²
Openings: 1 door (1.89) + 2 windows (2 × 1.44 = 2.88) = 4.77 m²
Net area: 45 − 4.77 = 40.23 m²
Litres before wastage: (40.23 × 2) ÷ 13 = 6.19 L
With 10% wastage: 6.19 × 1.10 = 6.81 L
Buy: 1 × 4 L + 3 × 1 L = 7 L (0.19 L spare)

Exterior wall, weathershield, extra wastage

Wall-area mode: 60 m², 2 coats, weathershield 9 m²/L, 15% wastage
Litres before wastage: (60 × 2) ÷ 9 = 13.33 L
With 15% wastage: 13.33 × 1.15 = 15.33 L
Least leftover: 4 × 4 L = 16 L (0.67 L spare)
Fewest tins: 1 × 20 L bucket (4.67 L spare) — fewer to carry, more waste

Small room + ceiling, one coat over old paint

Room 3 × 3 m, height 2.7 m, ceiling included, openings override 3.0 m²
Gross: 2 × (3 + 3) × 2.7 + 3 × 3 = 32.4 + 9 = 41.4 m²
Net area: 41.4 − 3.0 = 38.4 m²
Litres before wastage: (38.4 × 1) ÷ 13 = 2.95 L
With 10% wastage: 2.95 × 1.10 = 3.25 L
Buy: 1 × 4 L = 4 L (0.75 L spare)

Frequently asked questions

Sources & references

Spreading rate is a product-specific figure printed on each tin's data sheet; the category defaults here are typical published values and are editable. Defaults and tin sizes were last cross-checked on 2026-07-11.

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