Wall Paint Calculator.

Introduction to Wall Area & Paint Planning

Whether you are painting a single accent wall or updating an entire hallway, calculating the exact surface area is the first step. By calculating your wall area and subtracting non-paintable items like doors and windows, you can determine exactly how much paint you need, reducing wasted paint and saving money.

The Mathematical Formula

To find the net paintable area of a wall, we compute the gross wall area and subtract all cutouts:

Gross Area = Length × Height
Net Area = Gross Area - Sum of (Door & Window Areas)

Typically, standard doors are estimated at **21 sq ft (3 × 7 ft)**, and standard windows are estimated at **15 sq ft (3 × 5 ft)**.

Step-by-Step Example Calculation

Suppose you want to paint a wall with a length of **15 feet** and a height of **9 feet**, which contains **1 door** and **2 windows**:

1. Calculate gross area: 15 ft × 9 ft = 135 sq ft.
2. Sum the deductions: 1 door (21 sq ft) + 2 windows × 15 sq ft (30 sq ft) = 51 sq ft.
3. Subtract deductions: 135 sq ft - 51 sq ft = 84 sq ft net paintable area.
4. Calculate paint volume: At a standard coverage of 350 sq ft/gal, a single coat needs 84 ÷ 350 = 0.24 gallons. For 2 coats, you need approximately 0.48 gallons.

Common Mistakes

• Forgetting the primer: Raw drywall and dark paint colors absorb more liquid. Always apply primer or plan for extra paint.
• Double-counting windows: Make sure you only deduct windows and doors that are completely contained within the wall area you are calculating.