Room Paint Estimator

How to calculate Room Paint Estimator?

The estimator computes the paintable surface by adding wall and ceiling areas, subtracting doors and windows, then accounting for the number of coats.

Key formula: total_paintable_area = wall_area + ceiling_area - total_door_area - total_window_area total_area_all_coats = total_paintable_area * coats gallons_needed = ceil(total_area_all_coats / paint_coverage_per_gallon)

Using the Room Paint Estimator calculator: an example

Example values: 12 ft (length) × 10 ft (width) × 8 ft (height), 2 doors (6.8×2.5 ft), 2 windows (3×4 ft), 2 coats, 350 sq ft/gal.

Step-by-step calculation:

• Compute walls: perimeter = 2×(12+10)=44 ft → wall_area = 44×8 = 352 sq ft. Compute ceiling: 12×10 = 120 sq ft.
• Subtract openings: doors = 2×(6.8×2.5)=34 sq ft; windows = 2×(3×4)=24 sq ft. total_paintable_area = 352+120−34−24 = 414 sq ft.
• Apply coats: total_area_all_coats = 414 × 2 = 828 sq ft.
• Calculate gallons: gallons_needed = ceil(828 / 350) = ceil(2.37) = 3 gallons (round up and allow extra for touch-ups).

Frequently Asked Questions

Should I include the ceiling?

Include the ceiling only if you plan to paint it; otherwise leave ceiling area out. The calculator supports both approaches by using the ceiling input.

Do trim, baseboards, or closets affect the estimate?

Trim and detailed work are typically not included. If you need paint for trim, estimate separately or add a small percentage (5–10%) to the final quantity.

Should I round up the gallons?

Yes. Always round up to the next full gallon and consider buying an extra quart for touch-ups and color matching.