Paint Calculator
Estimate the paint quantity and budget required for your walls or entire rooms.
Single Wall
Entire Room
Interior
Exterior
💡 Smart Tips
For rough or dark surfaces, consider adding an extra coat.
Standard coverage is approx. 100 sq ft (10 sq m) per litre per coat.
Ultimate Paint Planning Guide: The Science of Coverage
Why Your "Guess" Will Fail
Paint estimation is not just simple multiplication; it is a chemistry problem. Most homeowners make the mistake of using the "400 sq ft per gallon" rule of thumb found on the side of a paint can. In reality, that number assumes a perfectly smooth, non-porous, pre-primed surface applied by a machine.
The GetEzzy Paint Calculator is engineered to solve the "Real World" variable. By accounting for Surface Drag, Absorption Rates, and Coating Opacity, we provide a number that keeps your roller wet until the very last corner.
Mastering the Tool: A Deep Dive
To get a contractor-grade estimate, precise input is key. Here is how to leverage every feature of our interface:
1. The Unit Toggle System
We support both Imperial (ft) and Metric
(m) because the construction industry is split.
Note: When you switch units, our tool doesn't just convert the input numbers; it
adjusts the deeper constant variables for "Standard Openings." In Metric mode, a door is
calculated as exactly 1.86m², whereas in Imperial, it's 20 sq ft. This subtle adjustment ensures
local standard sizing accuracy.
2. Multi-Room Logic
Painting a whole house? Don't calculate one room at a time. Use the + Add Another Room button.
- Benefit: This aggregates the total surface area *before* rounding. If Room A needs 3.2L and Room B needs 3.2L, calculating separately means buying 4L + 4L (8L). Calculating together means 6.4L, or buying 7L. You save money by batching.
- Ceiling Toggle: Each room has an individual "Include Ceiling" checkbox. Use this for bedrooms but uncheck it for bathrooms where you might have tiles or a different moisture-resistant ceiling paint.
3. Opening Deductions (The Hidden Money Saver)
Standard calculators ignore windows, leading to 15-20% over-purchasing. We aggressively deduct:
- Doors: We assume standard 7ft × 3ft interior doors. For double doors, simply increment the counter by 2.
- Windows: We standardize at 5ft × 3ft. If you have a massive "Picture Window," count it as 3 standard windows to subtract the correct glass area.
Why do we calculate 2 coats when 1 looks fine? Why is Exterior paint factored differently? Here is the science:
1. Surface Porosity & Drag
New drywall acts like a sponge. It has high porosity. The first coat you apply is largely absorbed into the gypsum and paper face, providing very little color coverage. This is the "Sealer" coat.
- Interior Emulsion: Formulated with finer particles. It creates a smooth film. Our spread rate of 100 sq ft/L assumes a primed surface. If unprimed, efficiency drops to 60%.
- Exterior Acrylic: These paints contain "elastomers" to stretch with heat/cold. They are thicker and have higher "drag" on the roller, reducing coverage efficiency to 90 sq ft/L.
2. Opacity & The "Hiding Power"
Not all liters are equal. Cheap paints use cheap fillers (clay/calcium) that become translucent when dry. Premium paints use Titanium Dioxide (TiO2) for opacity.
The "3rd Coat" Rule: If you are changing from a Dark Color (e.g., Navy Blue) to a Light Color (e.g., Cream), 2 coats will NOT hide the dark base. The physics of light reflection means the dark pigment will absorb light through the topcoat. You MUST manually set the tool to 3 Coats in this scenario.
3. The Wet Edge Algorithm
We calculate a buffer because of the "Wet Edge" rule. You must keep the roller stroke wet to blend lines. If you stop because you ran out of paint, and the edge dries, you will see a permanent "Lap Mark" when you resume. Our "Rounding Up to 0.5L" ensures you never run dry mid-wall.
// The Logic Sequence:
1. Net Area = (Walls × H) - (Doors + Windows)
2. Load Area = Net Area × Coat Count
3. Raw Litres = Load Area / Material_Spread_Rate
4. Purchased Units = CEILING(Raw Litres, 0.5)
Pro-Tips for a Perfect Finish
Never paint straight from the can. If you buy 3 separate cans of "Antique White," slight manufacturing variations can make them look different. "Boxing" means pouring all 3 cans into one large bucket and mixing them. This averages out the color for a uniform finish.
External Painting: Never paint if humidity is > 85% or temp is < 10°C. The binder won't knit properly, leading to early flaking. Our estimate holds true only for ideal drying conditions.
Troubleshooting Results
"The cost seems too low."
Our tool uses a median price of ₹400/L (approx $20/gallon). Premium paints like Royal Emulsion or Velvet Touch can cost 3x this amount. Always check the actual price on the tin and input it in the "Cost per Litre" optional field for accuracy.
"I have a textured 'Popcorn' ceiling."
Texture increases surface area by 30-50% compared to a flat ceiling. If you are painting texture, treat it like an "Exterior" surface in our calculator or simply add 1 extra coat to the count to force the math to supply more material.
⚠️ Material Warning
This calculator estimates PAINT only. It does not calculate Primer, Wall Putty, or Thinners. For a new bare wall, the general rule is: 1 Litre Primer for every 2 Litres of Topcoat.