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What is a Paint Calculator?
A Paint Calculator works out how many litres of paint you need to cover a room's walls, based on the room's dimensions, the number of coats, and the paint's coverage rate. This is a practical tool for Indian homeowners getting quotes from painters or buying paint tins directly — most brands print a coverage rate in sq m/litre on the tin label, which you can plug straight into this calculator.
Formula
Paint Required (Litres) = Wall Area ÷ Coverage Rate (sq m/litre)
The formula treats the room as a rectangular box, sums the perimeter (2 × (L+W)) times the height for total wall surface, then multiplies by the number of coats since each coat needs its own paint. The default coverage rate is 10 sq m/litre — a common mid-range emulsion figure — but enter your tin's exact rate for a more precise result.
Worked Example
For a room 5 m long, 4 m wide, 3 m high, with 2 coats and a coverage rate of 10 sq m/litre:
Paint Required = 108 ÷ 10 = 10.8 litres
So this room needs about 10.8 litres of paint for two coats — typically rounded up to two 4-litre tins plus one 2-litre or 3-litre tin, depending on what pack sizes your brand offers.
How to Use This Calculator
- Enter the room's length, width, and height in metres.
- Enter the number of coats you plan to apply (2 coats is standard for a fresh finish over primer).
- Enter the paint's coverage rate in sq m per litre — check the tin label, or leave the default of 10.
- Click Calculate to see the total litres and wall area.
Things to Know
- Textured or rough (unplastered) walls absorb more paint, so their real coverage rate can be 20-30% lower than the tin's stated figure — factor this in for older constructions.
- Always buy a little extra (5-10%) for touch-ups after move-in, since exact colour-matching a repeat batch later can be tricky.
- Pair this with the Flooring Calculator and Tile Calculator for a complete room renovation budget.
From Litres to a Full Painting Budget
Knowing the litres needed is only half the job of budgeting a paint job. Multiply the litre figure by your chosen paint's per-litre price to get the material cost, then add labour — Indian painters typically charge per square foot of wall area or a flat day rate, so the wall area this calculator computes is directly useful when getting quotes. Primer is a separate cost on new or repainted walls in a different shade, and is usually applied as one coat before the topcoat colours — budget it as an additional line item rather than folding it into your topcoat litre estimate. Textured finishes, stencil work, or accent walls in a premium shade typically cost more per litre and take longer to apply, so get a separate quote for any wall that isn't a simple flat colour. Lastly, always round your litre requirement up to the next full tin size your brand sells (1L, 4L, 10L, 20L) rather than trying to buy an exact fractional quantity.
More Worked Examples
Small bedroom, single coat touch-up: A 3.5 m × 3 m bedroom, 2.8 m high, needing just 1 coat of touch-up paint at a coverage rate of 10 sq m/litre.
Paint Required = 36.4 ÷ 10 = 3.64 litres
A single 4-litre tin covers this comfortably with a small amount left over for future touch-ups — a good example of how a single coat over an existing colour needs far less material than a full 2-coat repaint.
Large living-cum-dining hall: A 7 m × 6 m open hall, 3.2 m high, with 2 coats and a premium emulsion rated at 12 sq m/litre (premium paints often cover slightly more per litre than budget emulsions).
Paint Required = 166.4 ÷ 12 = 13.87 litres
This typically translates to three 4-litre tins plus a small 1-2 litre top-up, or one 20-litre bucket if your brand offers bulk packaging for large rooms — bulk buckets usually work out cheaper per litre than multiple smaller tins.
Two-BHK flat, whole-house repaint: A homeowner repainting an entire 2-BHK apartment might run this calculator room-by-room — say a combined wall area across bedrooms, hall, and kitchen of 240 m² with 2 coats at 10 sq m/litre.
At a typical mid-range emulsion price of ₹280-350 per litre, this puts the material cost alone somewhere around ₹6,700-8,400, before adding primer, labour, and any accent-wall upcharges — a realistic starting estimate when comparing painter quotes for a full-flat repaint in most Indian cities.
Frequently Asked Questions
Q: Does this calculator account for doors and windows when computing wall area?
A: No, it calculates the full wall area as if the room were a solid box with no openings. For rooms with large doors or windows, subtract roughly 1.5-2 m² per standard opening from the result to avoid over-buying paint.
Q: How many coats of paint should I plan for?
A: Two coats is standard for a fresh, even finish over a primed wall; a single coat may suffice for a minor touch-up in the same existing colour, while a major colour change (especially dark over light) may need a third coat for full opacity.
Q: Where do I find my paint's exact coverage rate?
A: Check the tin label — most paint brands print a coverage figure in square metres per litre (or square feet per litre) based on a smooth, primed surface; enter that exact figure instead of the default 10 sq m/litre for a more precise estimate.
Q: Why would my actual paint usage be higher than this calculator's estimate?
A: Textured, rough, or previously unpainted (bare plaster) walls absorb significantly more paint than a smooth primed surface, sometimes 20-30% more, so their real coverage rate is lower than the tin's stated figure.
Q: Should I buy extra paint beyond this calculator's result?
A: Yes, buying an extra 5-10% is wise for future touch-ups, since exact colour-matching a repeat batch later — especially after a tin has been discontinued or reformulated — can be difficult or impossible.
📅 Last reviewed: July 2026 · Formulas verified against RBI/SEBI/IT Dept guidelines.