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Paint Calculator

Calculate paint coverage — gallons, coats and containers for US interior and exterior painting. Enter drywall dimensions to get instant results. Enter dimensions, select units and add waste to get instant, supplier-ready numbers.

1. Measurements & Dimensions

2. Material Properties & Waste Allowance

3. Optional Material Cost

PAINT CALCULATOR ESTIMATE
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Enter dimensions above to calculate

Calculation Breakdown & StepsFormula: Wall area = 2 × (room length + room width) × wall height − excluded area; paint = area × coats × allowance factor / coverage.
  1. Enter values to see step-by-step substitution.

    Engineering Assumptions:

    • Four rectangular walls; ceiling and trim are excluded. Measure recesses and extra walls separately.
    • Coverage is a product- and surface-specific example, per coat. Rough or porous surfaces may need more paint. Container price is the price of one entered container size.
    VISUAL GUIDE — PAINT CALCULATORdrywall · paint-calculator

    TOP VIEW — Length × Width

    Paint Calculator topLength 23ftWidthPaint23×10 = 230 ft²

    SECTION — Room wall height 4ft

    Paint Calculator sectionPaint 4ft4"Wall area = 2 × (room length + room width) × wall height − excluded area; paint = area × coats × allowance factor / coverage. · +12% → 3.18 yd³
    Paint Calculator — Wall area = 2 × (room length + room width) × wall height − excluded area; paint = area × coats × allowance factor / coverage. · example 23×10 @4ft = 76.7 ft³ (2.84 yd³) → 3.18 yd³ with 12% waste · paint-calculator

    What Is This Calculator?

    The Paint Calculator — Estimates paint coverage for US interiors and exteriors — gallons, coats and containers from area and coverage.

    What Does It Calculate?

    • Net wall/ceiling area
    • Paint gallons with coats
    • Containers (ceil)
    • Cost with waste

    How to Use the Calculator

    1. Measure Room 12x10 ft, height 8 ft — use feet for length/width and inches for thickness where typical.
    2. Enter values and select units. The calculator converts to feet before calculating (inches /12, yards x3).
    3. Adjust waste % and optional price, then click Calculate. Results show with waste included.
    4. Use Reset to clear and try another size.

    Formula & Engineering Methodology

    Wall area = 2 × (room length + room width) × wall height − excluded area; paint = area × coats × allowance factor / coverage.

    • Area — Length x Width in ft2

    All units convert to exact standard engineering dimensions (NIST SP 811) before calculation to ensure consistency between US Customary and Metric measurements.

    Worked Example

    Example: Room 12x10 ft, height 8 ft

    STEPVALUE
    Wall area2x(12x8)+2x(10x8)=352 ft2
    Less openings-21 ft2 door =331 ft2
    Gallons @350 ft2/galceil(331/350)=1

    Construction Information

    Material: Drywall 4x8, screws 28 per sheet, tape 500 ft per roll. Paint 350 ft2/gal, primer 300. Spray foam 1 in = R6.

    • Measure longest x widest; split L-shapes into two rectangles and add.
    • Compact subgrade — soft spots add thickness.
    • For structural sizing (beams, headers, rebar) verify with a professional per local code.

    Material Information

    Drywall 4x8, screws 28 per sheet, tape 500 ft per roll. Paint 350 ft2/gal, primer 300. Spray foam 1 in = R6.

    Waste & Overages

    Add 10% for cuts and openings — 15% for vaulted ceilings.

    Practical Tips

    • Hang drywall perpendicular to joists
    • Prime before paint for true color

    Common Mistakes

    • Not deducting openings — over-order 10%
    • One coat paint — needs two for coverage

    Assumptions & Engineering References

    • Four rectangular walls; ceiling and trim are excluded. Measure recesses and extra walls separately.
    • Coverage is a product- and surface-specific example, per coat. Rough or porous surfaces may need more paint. Container price is the price of one entered container size.

    This calculator provides an estimate based on your inputs. Actual requirements vary by site, material and installation. For code-regulated or load-bearing work, consult a qualified professional.

    Calculations run 100% in your browser — zero tracking of your dimensions or input data.

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    Frequently asked questions

    What does the Paint Calculator calculate?

    The Paint Calculator estimates paint quantity for US jobs — Sheets (4x8 =32 ft2), Gallons at 350 ft2/gal, Insulation batts with waste. Enter dimensions, choose units, add waste and price to get instant results.

    How do I measure for paint?

    Measure room 12x10 ft, height 8 ft on site. Use the unit selectors — the tool converts inches→feet (÷12) and yards→feet (×3) before math. For non-rectangular, split into rectangles and add.

    How much waste should I add?

    Add 10% for cuts and openings — 15% for vaulted ceilings.

    How accurate is this paint estimate?

    Math is exact for your inputs. Actual needs vary by site, material and installation. Add 5–10% waste for rectangular, 10–15% for irregular.

    About Calculator Street

    Built by Vipul Otari for US homeowners & contractors. Calculator inputs are processed in your browser. Estimates depend on your measurements, product specifications and the assumptions shown on this page. Confirm order quantities with your supplier and structural requirements with your project designer. Page updated: 2026-09-11.

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