Paint Calculator

Our paint calculator uses professional painting industry standards to determine exactly how much paint you need for your room. Simply fill the fields and get the results.

How It Works

The foundation of all paint calculations is the coverage rate. In Nigeria and most parts of the world, paint manufacturers specify that 1 gallon of paint covers approximately 350 square feet of smooth wall surface. This is the industry-standard coverage rate our calculator uses.

Since Nigerian paint is sold in liters, we convert using the standard ratio: 1 gallon = 4 liters

Celiling Calcualtion

The ceiling is the simplest calculation because it has no obstructions like windows or doors.

Ceiling Area = Room Length × Room Breadth
Paint Needed (gallons) = Ceiling Area ÷ 350
Paint Needed (liters) = Gallons × 4

Example:

• Room: 30 feet × 18 feet
• Ceiling Area: 30 × 18 = 540 sq.ft
• Gallons needed: 540 ÷ 350 = 1.54 gallons
• Liters needed: 1.54 × 4 = 6.17 liters
• Purchase: 2 buckets of 4 liters (you’ll have about 1.83 liters leftover)

Wall Calculation

Wall calculation is more complex because we need to account for windows and doors that won’t be painted.

Step 1: Calculate Total Wall Area

Wall Area = 2(Height × Length) + 2(Height × Breadth)

This formula accounts for all four walls in a rectangular room.

Step 2: Calculate Window Area

Total Window Area = Number of Windows × (Window Width × Window Height)

Step 3: Calculate Door Area

Total Door Area = Number of Doors × (Door Width × Door Height)

Step 4: Calculate Paintable Wall Area

Paintable Area = Total Wall Area – Window Area – Door Area

Step 5: Calculate Paint Needed

Paint Needed (gallons) = Paintable Area ÷ 350
Paint Needed (liters) = Gallons × 4

Example:

• Room: 30 feet × 18 feet, Height: 10 feet
• 2 windows (3×5 ft each), 2 doors (3×7 ft each)
• Total Wall Area: 2(10×30) + 2(10×18) = 600 + 360 = 960 sq.ft
• Window Area: 2 × (3×5) = 30 sq.ft
• Door Area: 2 × (3×7) = 42 sq.ft
• Paintable Area: 960 – 30 – 42 = 888 sq.ft
• Gallons needed: 888 ÷ 350 = 2.54 gallons
• Liters needed: 2.54 × 4 = 10.15 liters
• Purchase: 3 buckets of 4 liters OR 1 bucket of 20 liters

Double Coat Calculation

When painting over a different color or on new drywall, professional painters recommend two coats for proper coverage and color saturation.

Double Coat Paint = Single Coat Amount × 2

Using our wall example above with double coat:

• Single coat: 10.15 liters
• Double coat: 10.15 × 2 = 20.30 liters
• Purchase: 1 bucket of 20 liters + 1 bucket of 4 liters Smart Bucket Recommendations

Our calculator doesn’t just tell you how many liters you need, it tells you exactly which buckets to buy at the store:

For quantities up to 4 liters: 1 bucket of 4 liters

For 4-8 liters: 2 buckets of 4 liters

For 8-12 liters: 3 buckets of 4 liters

For 12-20 liters: 1 bucket of 20 liters (more economical than 5 small buckets)

For 20-24 liters: 1 bucket of 20 liters + 1 bucket of 4 liters

For 24+ liters: Multiple 20-liter buckets as needed

This ensures you buy the most cost-effective combination while having enough paint to complete your project.

Step 1: Measure Your Room Measuring Length and Breadth:

Step 2: Enter Room Dimensions

Step 3: Count and Measure Windows

Step 4: Count and Measure Doors

Step 5: Choose Paint Options

Step 6: Click the “Calculate” button to generate your results instantly.

Step 7: Review Your Results

Frequently Asked Questions (FAQs)

How accurate is this paint calculator?
Our calculator uses the industry-standard coverage rate of 350 sq.ft per gallon, which is what professional painters use. Results are highly accurate for standard smooth walls. Textured walls or porous surfaces may require 10-15% more paint.

What if I’m painting multiple rooms?
Calculate each room separately, then add the totals together. This is especially important if rooms have different dimensions or if you’re using different colors.

Can I use this calculator for exterior walls?
This calculator is designed for interior walls. Exterior walls often require special weather-resistant paint with different coverage rates. Consult with your paint supplier for exterior projects.

What if my room isn’t rectangular?
Break irregular spaces into rectangular sections. Calculate each section separately, then add the paint requirements together. For L-shaped rooms, divide into two rectangles.

Should I measure in feet or meters?
Our calculator uses feet, which is the standard in Nigerian construction. If you measured in meters, convert to feet first (1 meter = 3.28 feet).

What if my walls are different heights?
Use the tallest wall measurement for your calculation. It’s better to have slightly extra paint than to run short.

What if I have different sized windows in the same room?
Calculate the room twice using different window sizes, or manually add the areas. For example, if you have 2 windows at 3×5 and 1 window at 5×5, you could run two calculations and note the difference.

What about built-in wardrobes or cabinets?
 Treat built-in furniture like large windows or doors. Measure the width and height of the built-in unit and add it to your door count, using the “custom” approach or closest size match.

What if I’m painting the doors and windows too?
If you’re painting the doors and window frames, don’t deduct them from your wall calculation. Just enter “0” for the number of doors and windows in the calculator.

Does the type of paint affect how much I need?
Yes, slightly. Our calculator uses standard emulsion paint coverage. Gloss paint often covers slightly more, while matte paint may require more. Stick with the calculator’s recommendations for emulsion paint.

What’s the difference between primer and paint?
Primer is applied before paint on new walls. Our calculator calculates finish paint only. If using primer, you’ll need a similar amount of primer as your first coat of paint.

Should I buy expensive or cheap paint?
Paint quality affects coverage. Cheap paint may require more coats, ultimately costing more. Medium to high-quality paint usually matches our calculator’s coverage rate.

Can I skip the second coat to save money?
You can, but the finish may look uneven or streaky, especially with color changes. The first coat often appears blotchy until the second coat evens it out.

Does double coat mean I paint twice?
Yes. Apply the first coat, let it dry completely (usually 4-6 hours), then apply the second coat. Our calculator accounts for both coats in the total paint needed.