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Full itemised cost — foundation to paint. Economy to premium grade.
🎨 Emulsion · Primer · Weathercoat · Enamel · Texture · Distemper
Paint Calculator
Calculate the exact litres of paint needed for any room — walls, ceiling, multiple coats. Supports interior emulsion, exterior weathercoat, primer, enamel, texture and distemper. Instant tin count and cost estimate.
Includes 10% wastage buffer · Door deduction: 1.8 m² each · Window deduction: 1.2 m² each
Wall Paint Quick Reference
Wall Area Formula
2×(L+W)×H − doors − windows
Litres Formula
(Area × coats ÷ coverage) × 1.10
Emulsion Coverage
14 m²/L (interior)
Wastage Buffer
10% added automatically
How to Use
- 1Select your paint type — Emulsion (Interior), Weathercoat (Exterior), Primer, Enamel, Texture, or Distemper. The coverage rate updates automatically.
- 2Choose your dimension unit (Feet or Metres) and set the number of coats.
- 3Select your currency and enter the price per litre from your supplier for a cost estimate.
- 4Toggle 'Include ceiling in calculation' on or off depending on your project.
- 5Enter room dimensions: Length, Width, and Height, plus the number of doors and windows.
- 6Click 'Add Room' to include additional rooms. The calculator sums all rooms for a combined total.
- 7Review the results: Total Area, Total Litres, recommended tin combination, and Total Cost.
Wall Paint Formula & How It Works
📐 Area Calculation
Wall area = 2 × (Length + Width) × Height
− (Doors × 1.8 m²)
− (Windows × 1.2 m²)
Ceiling = Length × Width (if toggled on)
Total area = Wall area + Ceiling area
(summed across all rooms)🪣 Litres & Cost
Litres needed =
(Total area × Coats)
÷ Coverage rate (m²/L)
× 1.10 ← 10% wastage buffer
Total cost =
Litres needed × Price per litre
Tins = optimised 1L + 4L + 10L + 20L
combination to minimise wastePaint Coverage Reference (per coat)
| Paint Type | Coverage Rate | Typical Use |
|---|---|---|
| Interior Emulsion | 14 m²/L | Interior walls, living rooms, bedrooms |
| Exterior Weathercoat | 11 m²/L | Exterior walls, exposed surfaces |
| Primer / Sealer | 12 m²/L | New plaster, bare surfaces, pre-coat |
| Enamel / Gloss | 15 m²/L | Doors, grills, metal, woodwork |
| Texture Paint | 5 m²/L | Decorative feature walls |
| Distemper | 10 m²/L | Budget interior finish |
Coverage rates are standard industry estimates. Rough, porous, or unpainted surfaces absorb more paint — add 10–15% extra on top of the wastage buffer for such surfaces. Source: Berger Paints Bangladesh technical data sheets; Asian Paints application guidelines.
Example Calculation for Wall Paint
🏠 Bedroom — Interior Emulsion
Room size12 ft × 10 ft × 10 ft
Wall area: 2×(12+10)×10440 ft² = 40.9 m²
2 doors: −2 × 1.8 m²−3.6 m²
1 window: −1 × 1.2 m²−1.2 m²
Ceiling: 12×10 ft+11.1 m²
Net paintable area47.2 m²
2 coats: 47.2×2 ÷ 146.74 L
+10% wastage= 7.42 L
Buy1×4L + 4×1L = 8L
🏗️ Exterior — Weathercoat
Wall area (net)120 m²
Coats2 (after primer)
Coverage11 m²/L
Base: 120×2 ÷ 1121.8 L
+10% wastage= 24 L
Buy1×20L + 1×4L = 24L
Cost @ BDT 350/L≈ BDT 8,400
Professional Painting Tips
- 1
Always Prime New Plaster Before Painting
New plaster is highly porous and alkaline. Applying finish paint directly causes uneven absorption, patchy colour, and poor adhesion. A primer coat seals the surface, improves adhesion, and reduces the finish coats needed — saving paint overall.
New wall total coats = 1 primer + 2 finish Total litres = (Area × 3) ÷ coverage × 1.10
- 2
Two Thin Coats Give a Better Finish Than One Thick Coat
Applying paint too thickly causes runs, uneven drying, and poor hide. Two thin coats dry faster, adhere better, and produce a smoother, more durable finish. Allow the first coat to dry fully (typically 2–4 hours for emulsion) before applying the second.
Recommended: 2 coats × (Area ÷ 14 m²/L) × 1.10
- 3
Use Weathercoat or Elastomeric for All Exterior Walls
Interior emulsion is water-based and not formulated to withstand rain, UV, humidity, or thermal expansion. It will fade, crack, and peel within one monsoon season on exterior surfaces. Always specify exterior-grade weathercoat or masonry paint for any outdoor wall.
Exterior coverage: 11 m²/L vs interior 14 m²/L Budget ≈ 27% more litres for exterior vs interior
- 4
Sand Lightly Between Coats for a Smooth Finish
After the first coat dries, lightly sand with fine-grit sandpaper (180–220 grit) to remove brush marks, dried drips, or dust nibs. Wipe down with a damp cloth before applying the second coat. This step is skipped by most painters but makes a significant difference to the final appearance.
Additional material cost: minimal (sandpaper only) Quality improvement: significant
- 5
Paint in the Morning or Evening — Avoid Direct Sunlight
Direct sunlight and high temperatures cause paint to dry too quickly, leaving lap marks and brush strokes. The ideal painting temperature is 10–35 °C. In Bangladesh's summer, start before 9 AM or after 4 PM for exterior work. Avoid painting just before or during rain — humidity prevents proper drying.
Ideal temp: 10–35 °C · Ideal humidity: <85% RH
- 6
Seal Leftover Paint Tightly for Touch-Ups
Colour-matching a future top-up batch is unreliable — even the same brand and code can vary slightly between production runs. Always seal leftover paint airtight, label it with the room name and date, and store upside-down for a few minutes to create an airtight seal. A 1L leftover tin can save significant rework cost later.
Recommended reserve: 1–2L per room for touch-ups
Frequently Asked Questions
How does the paint calculator work?
The calculator computes paintable area by taking wall area (2 × (Length + Width) × Height), subtracting standard deductions for doors (1.8 m² each) and windows (1.2 m² each), and optionally adding ceiling area (Length × Width). It then divides total area by the paint's coverage rate (m²/L), multiplies by number of coats, and adds a 10% wastage buffer. The final litre figure is rounded up and matched to the most efficient tin combination.
How many coats of paint do I need?
For new bare plaster: 1 primer coat + 2 finish coats is standard. For repainting the same colour: 2 coats is usually sufficient. For a colour change (dark to light or vice versa): 3 coats may be needed. For exterior walls using weathercoat: 2 coats after a primer. This calculator lets you set any number of coats — change the coats field to match your project.
What is the standard coverage rate for emulsion paint?
Coverage varies by paint type and surface condition. This calculator uses: Interior Emulsion 14 m²/L, Exterior Weathercoat 11 m²/L, Primer 12 m²/L, Enamel 15 m²/L, Texture Paint 5 m²/L, and Distemper 10 m²/L per coat. Actual coverage depends on surface porosity — rough or porous walls absorb more paint. The 10% wastage buffer accounts for minor overages.
How do I calculate paint for irregular or L-shaped rooms?
Split the irregular room into simpler rectangular sections. Use the 'Add Room' button to enter each section separately. The calculator sums all rooms and gives a combined total litres, tin recommendation, and cost. This works for L-shaped, U-shaped, or any multi-section space.
Should I include the ceiling in the calculation?
Include the ceiling if you are painting it with the same paint type as the walls. Toggle it off if you are using a separate ceiling paint, painting the ceiling white only, or leaving the ceiling unpainted. The calculator's ceiling toggle adds or removes Length × Width from the total paintable area.
How accurate is the litre estimate?
The estimate is accurate within 5–10% for standard smooth walls. Rough, textured, or very porous surfaces absorb significantly more paint — add an extra 10–15% for such surfaces beyond the built-in buffer. Old walls that have never been primed may require an extra coat. Very large ceiling areas may also need slightly higher coverage allowance depending on roller nap thickness.
Which tin sizes does the calculator recommend?
The calculator suggests the most efficient combination of 1L, 4L, 10L, and 20L tins to cover your total requirement with minimum waste. For large projects, 20L drums offer the best unit price. Always keep 1–2 small tins after the project for future touch-ups — colour-matching a repainted batch later is difficult and often imperfect.
What are current emulsion paint prices in Bangladesh?
Approximate 2024–25 market prices: Berger WeatherCoat Exterior BDT 320–400/L, Berger Easy Clean Emulsion BDT 280–350/L, Asian Paints Tractor Emulsion BDT 260–320/L, Nippon Paint Emulsion BDT 300–380/L. Prices vary by outlet and region. Always enter your actual supplier's current price per litre for an accurate cost estimate.
References & Data Sources for Wall Paint
- ↗Berger Paints Bangladesh — product coverage specifications for WeatherCoat and Easy Clean (2024 technical data sheets)
- ↗Asian Paints technical guidelines — interior and exterior coverage rates and application recommendations
- ↗BIS (Bangladesh Institute of Standards) IS 15489 — painting work in buildings, general guidance
- ↗BNBC (Bangladesh National Building Code) 2020 — painting and surface preparation for residential projects
Coverage rates are based on standard manufacturer data sheets. Actual consumption varies with surface condition, application method, and environmental conditions. Always verify prices with your local supplier. Last reviewed: May 2026.