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Find a simple solution to calculate how much paint you need
Planning a painting project can be exciting, but figuring out how much paint you’ll need is often a challenge. Whether you're refreshing a room's interior, updating your home's exterior, or working on a commercial project, understanding paint coverage is key to saving time and money. In this article, we’ll break down everything you need to know about paint coverage and how to calculate the amount of paint you need accurately.
Exterior Paint Coverage Per Litre
Exterior paints are formulated to withstand weather elements and often provide different coverage compared to interior paints. On average, 1 litre of exterior paint covers 8-10 square metres per coat.
However, the actual coverage can vary depending on factors like:
Surface type: Rough or porous surfaces such as brick and stucco absorb more paint, reducing coverage.
Color change: Painting over dark colors or using bold shades might require additional coats.
Paint quality: Higher-quality paints often provide better coverage, even with a single coat.
For most exterior projects, it's recommended to apply at least two coats to ensure durability and consistent color.
Calculating Paint for Exterior Surfaces
Exterior surfaces often include walls, trims, and additional architectural features like eaves or shutters. Here’s how to calculate the paint needed for exteriors:
Step 1- Measure the Wall Area:
Measure the height and width of each exterior wall and multiply them to calculate the area.
For example, if a wall is 4 metres high and 10 metres wide:
Wall Area = Height × Width = 4 × 10 = 40 square metres
Step 2- Include All Walls:
Add the areas of all the walls together to find the total wall area.
Step 3- Subtract Doors and Windows:
Measure and subtract the areas of any doors and windows to avoid overestimating.
For instance, if the total wall area is 150 square metres and there are 2 doors (1.9 square metres each) and 4 windows (1.5 square metres each):
Adjusted Wall Area = 150 - (2 × 1.9 + 4 × 1.5) = 138.4 square metres
Step 4- Account for Eaves and Trims:
Measure additional surfaces like eaves, trims, or gutters separately and add them to your total.
Step 5- Determine Total Coverage:
Multiply the total area by the number of coats required.
If two coats are needed:
Total Coverage = Adjusted Area × 2 = 138.4 × 2 = 276.8 square metres
Step 6- Calculate Paint Needed:
Divide the total coverage by the paint’s coverage per litre.
If 1 litre covers 9 square metres:
Litres Needed = 276.8 ÷ 9 ≈ 30.8 litres
Exterior Paint Calculator
Interior Paint Coverage Per Litre
Interior paints are designed for smooth, less porous surfaces. Typically, 1 litre of interior paint covers 10-12 square metres per coat. Key factors affecting coverage include:
Wall texture: Smooth walls require less paint, while textured or uneven walls consume more.
Primer usage: Applying a primer first improves paint coverage and reduces the number of coats needed.
Sheen type: Glossy or semi-gloss paints may provide slightly less coverage than matte or eggshell finishes.
Again, two coats are usually recommended for an even and professional finish.
How to Calculate the Amount of Paint You Need
To calculate how much paint you’ll need, follow these simple steps:
Step 1: Measure the Area
For Walls: Measure the height and width of each wall and multiply them to find the total area of each wall. For example, if a wall is 3 metres high and 5 metres wide:
- Wall Area = Height × Width = 3 × 5 = 15 square metres
Add the areas of all the walls together to get the total wall area.
For Ceilings: Measure the length and width of the ceiling and multiply them. For example, if the ceiling is 4 metres long and 3 metres wide:
- Ceiling Area = Length × Width = 4 × 3 = 12 square metres
Step 2: Subtract Doors and Windows
Deduct the areas of doors and windows to avoid overestimating. For example:
Standard door: ~1.9 square metres
Standard window: ~1.5 square metres
For example, if your total wall area is 50 square metres, and you have one door and two windows:
- Adjusted Wall Area = 50 - (1.9 + 2 × 1.5) = 45.1 square metres
Step 3: Determine Coats Required
Multiply the total area (wall and/or ceiling) by the number of coats you plan to apply. For instance:
If your total wall area is 45.1 square metres and you need two coats:
- Total coverage needed = 45.1 × 2 = 90.2 square metres
Step 4: Divide by Paint Coverage
Divide the total coverage required by the paint's coverage per litre. For example:
If the paint covers 10 square metres per litre:
- Litres needed = 90.2 ÷ 10 = 9.02 litres
Interior Paint Calculator
Examples for Common Properties
|
Property Type |
Walls (Litres) |
Ceilings (Litres) |
Exteriors (Litres) |
Total Paint (Litres) |
|
A Unit of 100 sqm with 2 Bedrooms |
12 |
8 |
N/A |
20 |
|
A Double-Story Town house of 160 sqm with 3 Bedrooms |
20 |
12 |
20 |
52 |
|
A House of 200 sqm with 4 Bedrooms |
26 |
14 |
25 |
65 |
Additional Tips
Buy extra paint: Always have an extra 10-15% on hand for touch-ups or mistakes.
Use a paint calculator: Many brands offer online tools to estimate your paint needs based on room dimensions and other factors.
How Can I Calculate the Cost of Paint?
Once you know how much paint you need, calculating the cost is straightforward. Here’s how to estimate:
Step 1- Find the Price Per Litre:
Check the price of the paint you’re planning to buy. For instance, if a 4-litre can costs $80:
Price per litre = $80 ÷ 4 = $20 per litre
Step 2- Multiply by the Total Litres Needed:
If your project requires 15 litres:
Total cost = 15 × $20 = $300
Step 3- Add Extra Costs:
Include additional costs for primer, brushes, rollers, or other materials.
Step 4- Consider Discounts or Rebates:
Look out for sales or bulk purchase discounts to save money.
Step 5- Budget for Overages:
Always add 10-15% to your estimate to cover unforeseen needs.
