Room Dimensions
Deductions
Results
341 ft²
Net Paintable Wall Area
Gross wall area
416 ft²
Window deductions
−24 ft²
Door deductions
−21 ft²
Ceiling area
168 ft²
Total paintable (walls + ceiling)
509 ft²
Floor area
168 ft²
Room perimeter
52 ft
How to measure a room for painting
- Measure each wall — Use a tape measure along the base of each wall. For rectangular rooms, you only need length and width (the calculator handles the perimeter math).
- Measure ceiling height — Measure from floor to ceiling in a corner. If the height varies, measure the lowest point.
- Count windows and doors — Standard windows deduct about 12 ft² each, standard doors about 21 ft². For unusual sizes, measure width × height.
- Check for vaulted ceilings — If one or both walls have a triangular gable above the standard ceiling line, measure the peak height and use the vaulted ceiling option above.
Common measurement mistakes
- Measuring floor area instead of wall area — A 12×14 room has 168 ft² of floor but 416 ft² of wall area (at 8ft ceilings). Floor area and wall area are very different numbers.
- Forgetting closet walls — If you're painting inside closets, measure those walls separately and add them to your total.
- Ignoring vaulted ceilings — A vaulted ceiling adds triangular gable area to the walls. A room with a 12ft peak on a 14ft wall adds about 28 ft² of extra wall area.
- Not accounting for texture — Textured walls (orange peel, knockdown) have 10–15% more actual surface area than smooth walls. This doesn't affect measurement but does affect paint quantity.
Wall area formulas
Rectangle room: Wall Area = 2 × (Length + Width) × Ceiling Height, minus window and door areas.
Vaulted gable: Gable Area = ½ × Wall Width × (Peak Height − Ceiling Height). Add this for each gable wall.