How much paint you actually need, and why painting quotes differ

Painting looks like the simplest job in a renovation, which is exactly why the quotes are so hard to compare. One painter says ₹14 a sq ft, another says ₹19, and a third gives you a lump sum for the flat. They may all be charging roughly the same. Or one of them may be leaving out the putty, and you'll find out when the walls look patchy after the second coat.

The way through is to do two things yourself: measure the area, and know what goes on the wall before the paint does. Then the quotes become arithmetic.

Measuring the paintable area

For a rectangular room, the four walls are 2 × (length + width) × height. Subtract doors and windows, since you're not painting them with wall paint. Add the ceiling, which is simply length × width, if it's being painted too.

Say you have a 2BHK and you're painting the living room and both bedrooms. All three have 10 ft walls.

Walls plus ceilings come to 1,340 + 456 = 1,796 sq ft. That's the number every quote should be measured against. Notice it's nowhere near the flat's carpet area multiplied by some round factor. Some painters quote that way, and it's a legitimate shortcut for them, but it means the "area" in their quote and the area on your wall are two different things.

Here's how that plays out. Say a whole flat measures 2,600 sq ft of actual paintable surface. Painter A quotes ₹14 per sq ft on carpet area of 1,000 sq ft × 3.5 = 3,500 sq ft, which is ₹49,000. Painter B measures the walls and quotes ₹19 per sq ft on 2,600 sq ft, which is ₹49,400. A's rate looks 26% cheaper. The totals are within ₹400 of each other.

The painting cost calculator does this measurement for you if you enter room length, width, height and openings, and it shows a cost per sq ft on the real area, which is the figure you want for comparing quotes.

Coverage: why the tin's number is optimistic

Every tin prints a coverage figure, something like "X sq ft per litre per coat". That number is real, but it's measured under conditions your walls won't meet: a smooth, sealed, primed surface, paint thinned exactly as recommended, and a film of the specified thickness applied evenly. Nothing is lost in the tray, nothing soaks into the plaster, and nobody goes back over a patch.

Real walls are more porous, especially old ones and anything with fresh plaster. Rollers and trays hold paint you'll never use. A colour change from dark to light, or a bright shade over white, can need an extra coat. My rule of thumb is to plan on about 80–85% of the printed coverage and accept a little left over, rather than run short and buy a second batch that doesn't quite match.

Back to the example. Suppose the wall paint says 120 sq ft per litre per coat and you want two coats on 1,340 sq ft of wall. On paper that's 1,340 × 2 ÷ 120 = 22.3 litres. If you plan on 100 sq ft per litre instead, it's 1,340 × 2 ÷ 100 = 26.8 litres. Paint comes in fixed pack sizes, so you'd end up buying something like 20 + 4 + 4 = 28 litres. The gap between 22 and 28 litres is the difference between finishing on Saturday and sending someone to the dealer on Saturday evening.

Ceilings usually get a cheaper, flatter paint. At the same 100 sq ft per litre, two coats on 456 sq ft is 456 × 2 ÷ 100 = 9.1 litres, so a 10 litre pack.

Putty and primer are where the money goes

On most jobs, the paint itself is the smaller part of the bill. Preparation and labour are the bigger part. The worked example on the painting calculator page shows this: prep and labour together are more than three-quarters of the cost before GST.

For a fresh wall, meaning new plaster or a wall stripped back, the usual sequence is a sealer or primer, two coats of putty sanded smooth, another coat of primer, and then two finish coats. Each putty coat has to dry before it's sanded, which is why fresh painting takes longer than people expect.

A repaint over sound existing paint is lighter. The walls are washed or sanded, cracks and dents are filled with putty only where needed, primer goes on the patched spots or the whole wall if the colour is changing a lot, and then the finish coats. If your walls are in decent shape, a repaint quote that includes two full coats of putty is charging for work your walls may not need. Ask.

This is the most common reason quotes differ. One painter's rate includes putty and primer; another's is paint and labour only, with prep added later as a separate line. Get every quote to say, in writing, how many coats of putty, how many of primer, how many of paint, and which product for each.

Damp walls and the monsoon

Paint over a damp wall fails. It bubbles, flakes, and grows a grey-green bloom in the corners within a season. In much of India the monsoon makes this a yearly problem: external walls with hairline cracks, a bathroom on the other side of a bedroom wall, a terrace above the top floor that has stopped shedding water properly.

The order matters. First find the source and fix it: seal the external cracks, redo the bathroom waterproofing, treat the terrace. Then let the wall dry out, which can take weeks after a heavy monsoon. Only then scrape back the loose paint, apply a damp-proof primer or treatment, and repaint. A painter who offers to just put a "waterproof" emulsion over a wet wall is selling you a repaint next year.

If you can, schedule interior painting for after the rains, and exterior painting for the dry months. It's not just about drying time. Moisture trapped behind paint is what causes most of the failures that get blamed on the brand.

Labour: per sq ft versus per day

Painters charge labour in two ways. Per sq ft means a fixed rate on the measured area, regardless of how long it takes. Per day means a daily wage for each painter, and you pay for however many days the job runs.

On the 1,796 sq ft example, labour at ₹15 per sq ft is 1,796 × 15 = ₹26,940. On a daily basis, three painters at ₹1,100 a day for 8 days is 3 × 1,100 × 8 = ₹26,400. Similar money, if the job takes 8 days. If it takes 11, it's 3 × 1,100 × 11 = ₹36,300. These rates are illustrative; use the ones you're quoted.

Per sq ft pushes the risk of slow work onto the contractor, which is why I'd prefer it for a whole-flat job. Per day can work well for small jobs, touch-ups, or where the scope is unclear, like a few damp patches that may need extra scraping. Either way, ask whether furniture moving, covering floors and cleanup are included, and whether the painter supplies ladders and scaffolding for double-height areas.

Putting a quote together

When you have the area, the coats, a realistic coverage figure, and the rates for paint, prep and labour, the total follows. The painting calculator takes all of these and also shows litres rounded up and a cost per sq ft. Do it once per contractor, using their stated prep and labour, and the cheapest quote is usually obvious, or the quotes turn out to be closer than they looked.

If painting is part of a bigger job, feed the total into the home renovation cost calculator alongside flooring, carpentry and the rest. Painting should normally be one of the last trades on site, after carpentry and electrical fittings, and the guide on budgeting a renovation covers that sequencing.

Take a measuring tape around the rooms you're painting this week, note the length, width, height and the size of each door and window, and run the numbers before the first painter visits. You'll know within five minutes whether their area is close to yours.