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Quick answer: paint (litres) = paintable area in sq ft × number of coats ÷ coverage per litre per coat, with the coverage taken from the tin or data sheet. A 12 × 10 ft room with 9 ft walls has about 479 sq ft of paintable wall and ceiling. At an assumed 120 sq ft per litre, two coats need about 8 litres, so a 10-litre pack covers touch-ups too.
The 120 sq ft per litre used here is illustrative, not a promise. Coverage claims apply to smooth, primed surfaces, and real coverage depends on the product, the surface, the colour change and the applicator.
Measure the Paintable Area: Walls, Ceiling and Openings
Walls: room perimeter × wall height. Subtract doors and windows, and add the ceiling area if it is painted. For a 12 × 10 ft room with 9 ft walls, the perimeter is 44 ft, so the walls are 396 sq ft. Deduct a 3 × 7 ft door (21 sq ft) and a 4 × 4 ft window (16 sq ft), leaving 359 sq ft, and add the 120 sq ft ceiling for 479 sq ft in total.
For rough planning, paintable area often lands around 3.5 to 4 times the floor area of an ordinary room, and this room comes out at 4.0 times. Use that only as a cross-check, never as the purchase quantity.
Convert Area to Litres: Coats and Coverage
Litres = area × coats ÷ coverage per litre. Coverage differs by layer: putty is quoted per kilogram for two coats, primer per litre for one coat, and emulsion per litre per coat. Read the value for each layer and product, and do not use one number for everything.
With an assumed 120 sq ft per litre, primer for 479 sq ft is about 4 litres and two coats of emulsion are about 8 litres. Add roughly 10% for touch-ups and losses to give 8.8 litres, so a 10-litre pack. Use 15 sq ft per kg for two putty coats only as a placeholder; the real figure is on the putty pack and rises sharply on rough plaster.
Why Real Coverage Differs From the Tin
Porous or rough surfaces absorb more paint, dark-to-light colour changes need extra coats, rollers and brushes spread differently, and thinning changes both hiding and film thickness. Textured exterior surfaces, high walls and windy weather increase consumption further.
Ask for a small test patch on the actual wall before you place the full order, and ask the applicator to record how much of the first wall was used.
Fix Damp and Cracks Before You Buy Paint
Paint over damp walls and it peels. Trace the leak first: a failed terrace, a leaking bathroom or a rising-damp problem needs repair, not another coat. See the terrace waterproofing guide and the bathroom waterproofing cost guide before painting adjacent walls and ceilings.
Let fresh plaster cure and dry as the paint maker advises, fill cracks and sand the putty, and use an alkali-resistant primer on new plaster. Prepare-surface time is where painters lose or save the most money.
Buying Rules: One Batch, One Shade Code, One Spare Litre
Buy all the tinted paint for a continuous area at one time and have the dealer tint the packs on the same machine, from the same base batch, and record the shade code. Tinted paints from different days can differ slightly, and once a wall is half painted the mismatch shows.
Keep a labelled litre for repairs, store it sealed away from heat, and note the room and date on the lid. Check the manufacturing date and confirm the product matches the specified system before the tins are opened.
Interior vs Exterior: What Changes in the Estimate
Exterior work usually needs a weather-resistant system, more coats or a heavier primer, scaffolding and dry weather, and rough or textured surfaces reduce coverage. In Mumbai, plan around the monsoon; in Delhi-NCR, avoid the hottest and most polluted days when dust affects the finish.
Include putty, primer, paint, masking, sandpaper and spares as separate lines in your construction material BOQ and tie the purchase date to the painting slot in the house construction stages checklist.
Paint Systems Compared: What Drives Consumption
| System | Layers usually planned | What raises consumption | What to confirm |
|---|---|---|---|
| New interior plaster | Putty (2 coats), primer, emulsion (2 coats) | Rough plaster, dark shade | Manufacturer's system on the data sheet |
| Repaint of a sound wall | Repair, primer, emulsion (2 coats) | Chalking or absorbent surface | Type of old paint underneath |
| Exterior weatherproof paint | Primer plus 2 coats | Texture, height, wind | Dry-weather window and access |
| Textured or designer finish | Base, texture, top coat | Pattern depth and tools | Sample panel signed off |
How to calculate before you order
- Measure walls and ceilings separately and subtract openings.
- List every layer: putty, primer, paint, plus repair materials.
- Read the coverage per litre or kg for each layer from the data sheet.
- Calculate litres as area × coats ÷ coverage per layer.
- Add a margin for rough surfaces and touch-ups.
- Fix leaks, cracks and damp before ordering.
- Buy tinted paint for one continuous area in one batch with a recorded shade code.
- Apply a sample patch and record how much the first wall consumed.
Compare current options and place orders onMadoverbuildings (MOB).
Pricing Snapshot
| Product | Live Price | MRP / RFQ | Buying Note |
|---|---|---|---|
| Sika Acrylic Primer Sikafloor-09 Primer 5kg (Pack of 1) | Rs 2,108.41 / Unit | MRP Rs 2,741 | RFQ Rs 2,108.41 | Stock: 100; Delivery: QWIK; Unit: Unit |
| Asian Paints TruCare Interior Wall Primer - Water Thinnable 20 Liters | Rs 3,250 / Unit | MRP Rs 4,010 | RFQ Rs 3,250 | Stock: 95; Delivery: QWIK; Unit: Unit |
| Asian Paints TruCare Metal Primer Yellow 20 Liters | Rs 4,815.98 / Unit | MRP Rs 5,970 | RFQ Rs 4,768.30 | Stock: 25; Delivery: QWIK; Unit: Unit |
| Asian Paints TruCare Wood Primer White 20 Liters | Rs 4,579.95 / Unit | MRP Rs 5,750 | RFQ Rs 4,534.60 | Stock: 25; Delivery: QWIK; Unit: Unit |
Wastage mistakes that short the last pour
- Do not buy paint by floor area alone; two rooms of the same size can have very different wall heights and openings.
- Ask the dealer for the shade code and base name and photograph the tin label.
- Mix packs of the same shade in one large container before starting a wall to even out small differences.
- Do not thin paint beyond the data sheet; it lowers hiding power and durability.
- Match the primer to the surface: new plaster, old paint and damp-prone walls need different primers.
- Record recoat times from the tin and do not rush the second coat.
How This Plays Out on Madoverbuildings (MOB)
Madoverbuildings (MOB) can help you source putty, primer, paint and related finishing materials once the system and quantity are confirmed. Explore relevant construction materials on MOB, submit a mixed list through Magic Quote, or use an RFQ for project quantities. Shade codes, batches, stock and delivery for the selected product should be confirmed before purchase.
Relevant Products to Compare
Frequently Asked Questions
How many litres of paint do I need for 1000 sq ft?
It depends on the paintable area, not the floor area. For 1,000 sq ft of wall area, two coats at an illustrative 120 sq ft per litre need about 17 litres. As a rough cross-check only, paintable area is often 3.5 to 4 times the floor area.
What is the coverage of paint per litre?
It varies by product and surface, and manufacturers quote it for smooth primed surfaces. Use the coverage on the tin or data sheet for each layer and add a margin for rough walls.
How many coats of paint are needed?
Most interior systems use one coat of primer and two coats of emulsion on prepared walls. Colour changes, poor surfaces and textured finishes may need more.
How much wall putty do I need per sq ft?
Use the coverage per kg for two coats on the pack. It varies widely and is much higher on rough plaster, so a small test area gives a better estimate than a rule of thumb.
How much primer do I need?
Primer is usually one coat. Divide the paintable area by the primer's coverage per litre on the data sheet and add a small margin.
Should I paint the ceiling with the same paint as the walls?
Not necessarily. Ceilings often use a different finish or shade. Calculate the ceiling area as a separate line so you buy the right quantity of the right product.
Should I buy all the paint at once?
For one continuous area, yes, in one batch with a recorded shade code to avoid visible mismatch. Keep a labelled litre for repairs.
Can I paint over damp walls?
No. Find and fix the source of moisture first, let the surface dry, and then prepare and paint. Painting over damp walls leads to peeling and blistering.
