Planning a paint project
Most interior jobs need two coats for even color, especially when covering a darker shade. Ceilings, closets, and accent walls change the total area—this tool assumes you paint all four walls plus the ceiling in one color.
Prep work (cleaning, patching, sanding, taping) affects how much paint actually covers. The calculator uses 10 m² per liter per coat as a default—your label may say 8 or 12.
What does this calculator estimate?
This tool estimates how many liters of paint you need for a rectangular room's four walls plus ceiling, then multiplies by your price per liter. It subtracts one standard door and one standard window opening from wall area—a rough planning figure, not a professional takeoff.
Real jobs vary with surface texture, color change, primer needs, and application method. Always check the coverage figure printed on your paint can.
Formula
Wall area = 2×(L×H) + 2×(W×H)
Net walls = Wall area − door (1.9×0.8 m) − window (1.2×1.0 m)
Total area = Net walls + ceiling (L×W)
Liters = (Total area × Coats) ÷ 10 m²/L
Cost = Liters × Price per liter
Worked examples
Small bedroom (metric)
Room 3.5×3×2.4 m · 2 coat(s) · $18/L
~7.82 L · ~$140.76 paint cost
After door/window deduction, ~39 m² painted twice at 10 m²/L ≈ 7.8 L. Round up to 8–9 L for touch-ups.
Living room, two coats
Room 5×4.5×2.7 m · 2 coat(s) · $22/L
~14.76 L · ~$324.72 paint cost
Larger wall footprint pushes liters above a single gallon-equivalent bucket—buy two containers or one large + one small for matching batch numbers.
Single coat refresh (same color)
Room 4×3.5×2.4 m · 1 coat(s) · $16/L
~4.31 L · ~$68.96 paint cost
One coat over a similar shade may be enough—still verify coverage on a test patch in your lighting.
Three coats (bold color change)
Room 3×3×2.4 m · 3 coat(s) · $20/L
~10.77 L · ~$215.40 paint cost
Deep colors on white walls often need three coats plus primer in practice—this estimate is a floor, not a ceiling.
Budget planning with sale paint
Room 4.2×3.8×2.5 m · 2 coat(s) · $12/L
~10 L · ~$120.00 paint cost
Cheaper paint may have lower coverage—if the label says 8 m²/L, divide area by 8 instead of 10 for a safer order quantity.
Common mistakes
Ordering exact liters with no margin
Open containers, roller absorption, and touch-ups consume extra. Buy 10–15% more.
Skipping primer on new drywall
Bare drywall drinks paint. Primer plus two finish coats beats three finish coats alone.
Ignoring ceiling if it stays white
If you are not painting the ceiling, subtract length × width from total area mentally.
Mixing unit systems
Feet for room size and liters for paint is fine only after converting feet to meters.
Related calculators
References
How This Calculator Works
Enter room size
Length, width, and height define the wall and ceiling surface area.
Apply coverage math
Total area × coats ÷ 10 m²/L gives an approximate liter count.
Multiply by price
Liters × cost per liter produces a rough materials budget.
What is Paint Cost Calculator?
A paint cost calculator estimates how much paint a room needs and what it will cost, using wall dimensions, the number of coats, and price per unit. It converts total wall area into required volume based on typical coverage per litre or gallon.
This tool totals wall and ceiling square meters, subtracts a standard door and window opening, applies your coat count, and converts to liters using 10 m² per liter. All math runs locally in your browser.
Walls + ceiling
Four walls and ceiling area from your room dimensions.
Fixed openings
One standard door and window subtracted from wall area.
Estimate only
Coverage varies by product—verify on the label before buying.
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How to Use This Tool
Measure the room
Enter length, width, and height in meters.
Set coats
Choose how many coats you plan to apply (often two for a color change).
Enter paint price
Add your local cost per liter from the store or online listing.
Calculate
Review wall area, total painted area, liters needed, and estimated cost.
Pro Tips
- Buy 10–15% extra paint for touch-ups and uneven surfaces
- Use primer when covering dark colors or bare drywall
- Test a sample patch in your room lighting before buying bulk
- Flat paint often covers better than high-gloss on large walls
- Ventilate the room and follow the manufacturer dry-time between coats