Paint Calculator
This professional-grade paint calculator helps homeowners, contractors, and facility managers estimate paint quantities for walls, ceilings, and trim—fast and accurately. Enter your room dimensions, openings, coats, and coverage to get exact gallons, a smart can breakdown, and optional cost estimates.
Results
Values update as you type. The totals include coats and the surface factor.
Tip: If you’re between sizes, consider buying a bit extra for touch-ups—especially with dark or highly saturated colors.
Data Source and Methodology
Authoritative Data Source: Benjamin Moore — Paint Calculator & Coverage Guidance (accessed 2025-09-15). See: https://www.benjaminmoore.com/en-us/paint-calculator.
Note: Manufacturers specify coverage on each product label; always defer to the product you intend to use.
Tutti i calcoli si basano rigorosamente sulle formule e sui dati forniti da questa fonte.
The Formula Explained
Wall area per room:
A_wall = 2(L + W)H - n_d A_d - n_w A_w - A_extra
Ceiling area per room (if included):
A_ceiling = L × W
Trim area per room (optional):
A_trim = \ell_{trim} × w_{trim}
Total equivalent paint area (including coats):
A_eq = A_wall × c_w + A_ceiling × c_c + A_trim × c_t
Effective coverage (adjusted by surface factor s%):
C_eff = C × (s / 100)
Paint required in gallons:
G = A_eq / C_eff
Glossary of Variables
- L, W, H: Room length, width, height.
- n_d, n_w: Number of doors and windows.
- A_d, A_w: Area of a typical door/window (defaults adjustable).
- A_extra: Any additional opening area to subtract (optional per room).
- c_w, c_c, c_t: Coats for walls, ceiling, and trim.
- ℓ_trim, w_trim: Total trim length and trim width.
- C: Label coverage (sq ft/gal or m²/L).
- s: Surface factor percent to account for porosity/texture.
- G: Total paint required in gallons.
How It Works: A Step-by-Step Example
Scenario: 15 ft × 12 ft room, 9 ft walls, 2 doors, 2 windows, include ceiling, no trim. Coverage 350 sq ft/gal. Coats: walls=2, ceiling=1. Surface factor s=100%.
- Compute wall area: 2(L+W)H = 2(15+12)×9 = 486 sq ft.
- Subtract openings: doors 2×21 = 42; windows 2×15 = 30; net walls = 486−42−30 = 414 sq ft.
- Ceiling area: L×W = 15×12 = 180 sq ft.
- Equivalent area: A_eq = 414×2 + 180×1 = 1008 sq ft-coats.
- Paint: G = 1008 / 350 = 2.88 gal. Recommend 3 gal or optimize with 2 gal + 4 quarts, based on price/availability.
Frequently Asked Questions (FAQ)
Do I need primer?
Primer is recommended on new drywall, stained surfaces, drastic color changes, or problem substrates. Primer coverage differs by product; add it as a separate calculation using the primer’s label coverage.
How do I estimate trim paint?
Enter the total linear length of baseboards/casings and set a typical width (e.g., 3.5 in). The tool converts linear length to area and applies trim coats.
What if my room isn’t perfectly rectangular?
Split it into multiple rooms or use the “Extra opening area” to subtract large features. For complex shapes, approximate by sections and add multiple rooms.
How precise are the can recommendations?
We search combinations of 5-gal, 1-gal, and quart cans to meet or slightly exceed the need with minimal waste. If prices are provided, we also minimize estimated cost.
Will rough surfaces affect the estimate?
Yes. Increase the surface factor from 100% to 110–130% for rough or porous surfaces; the calculator lowers effective coverage accordingly.
Can I save or print the results?
Use your browser’s print or export to PDF. We maintain a clear, printer-friendly layout.