{
  "slug": "exterior-paint-gallons-calculator",
  "title": "Exterior Paint Gallons Calculator",
  "heading": "Exterior Paint Gallons Calculator",
  "category": "other",
  "url": "https://www.revenuelab.fyi/toolbox/exterior-paint-gallons-calculator",
  "summary": "Estimate gallons of exterior house paint from wall dimensions and siding texture.",
  "description": "Exterior house paint follows the same core math as interior paint but with a lower typical coverage rate — often 250-350 sq ft per gallon rather than 350-400 — because textured siding like stucco, wood shakes, or heavily embossed vinyl soaks up more paint per square foot than a smooth interior drywall wall. This calculator takes your home's total exterior wall perimeter and average wall height to compute gross wall area, subtracts window and door openings, then divides by your chosen coverage rate (adjustable for siding texture) and multiplies by coat count, which is typically two coats for full exterior repaints and one for maintenance touch-ups over sound existing paint. Because exterior projects often span multiple stories, gable ends, and trim separate from the main field color, this tool focuses on the main wall field paint and assumes trim, fascia, and soffit paint are calculated and purchased separately since they're usually a different sheen or color. Buying slightly extra exterior paint is generally wiser than interior since exact color-matching outdoors, especially years later for touch-ups, is far more visible than an indoor mismatch.",
  "formula": "Wall Area = (Perimeter × Height) − Openings. Gallons = ceil((Wall Area × Coats) ÷ Coverage per Gallon).",
  "dateModified": "2026-09-06",
  "run_url": "https://www.revenuelab.fyi/api/public/calc?tool=exterior-paint-gallons-calculator",
  "inputs": [
    {
      "id": "perimeter",
      "label": "Exterior wall perimeter",
      "kind": "number",
      "hint": null,
      "default": 160,
      "unit": "ft",
      "min": 10,
      "max": null
    },
    {
      "id": "height",
      "label": "Average wall height",
      "kind": "number",
      "hint": null,
      "default": 9,
      "unit": "ft",
      "min": 6,
      "max": 40
    },
    {
      "id": "openings",
      "label": "Doors & windows area",
      "kind": "number",
      "hint": null,
      "default": 150,
      "unit": "sq ft",
      "min": 0,
      "max": null
    },
    {
      "id": "coats",
      "label": "Number of coats",
      "kind": "number",
      "hint": null,
      "default": 2,
      "unit": null,
      "min": 1,
      "max": 3
    },
    {
      "id": "coveragePerGallon",
      "label": "Coverage per gallon",
      "kind": "number",
      "hint": null,
      "default": 300,
      "unit": "sq ft",
      "min": 150,
      "max": 400
    }
  ],
  "outputs": [
    {
      "id": "gallons",
      "label": "Gallons of exterior paint",
      "format": "number",
      "hint": null,
      "primary": true
    },
    {
      "id": "wallArea",
      "label": "Net wall area",
      "format": "number",
      "hint": "sq ft",
      "primary": false
    },
    {
      "id": "rawGallons",
      "label": "Exact gallons before rounding",
      "format": "decimal",
      "hint": null,
      "primary": false
    }
  ],
  "worked_example": {
    "inputs": [
      "Exterior wall perimeter: 160 ft",
      "Average wall height: 9 ft",
      "Doors & windows area: 150 sq ft",
      "Number of coats: 2",
      "Coverage per gallon: 300 sq ft"
    ],
    "outputs": [
      "Gallons of exterior paint: 9",
      "Net wall area: 1,290",
      "Exact gallons before rounding: 8.6"
    ]
  },
  "how_to": {
    "title": "How to use this",
    "steps": [
      "Enter exterior wall perimeter (ft).",
      "Enter average wall height (ft).",
      "Enter doors & windows area (sq ft).",
      "Enter number of coats.",
      "Enter coverage per gallon (sq ft).",
      "Read your gallons of exterior paint on the right — it updates as you type.",
      "Hit Share to keep the scenario or send it to someone."
    ]
  },
  "scenarios": [
    {
      "name": "Conservative",
      "description": "Lower-end numbers — what if things land soft?",
      "values": {
        "perimeter": 95,
        "height": 9,
        "openings": 90,
        "coats": 1,
        "coveragePerGallon": 180
      }
    },
    {
      "name": "Typical",
      "description": "Defaults — the most common real-world setup.",
      "values": {
        "perimeter": 160,
        "height": 9,
        "openings": 150,
        "coats": 2,
        "coveragePerGallon": 300
      }
    },
    {
      "name": "Ambitious",
      "description": "Higher-end numbers — what if things really pop?",
      "values": {
        "perimeter": 255,
        "height": 9,
        "openings": 240,
        "coats": 3,
        "coveragePerGallon": 400
      }
    }
  ],
  "limitations": [
    "Estimates assume standard, average conditions — local rules, pricing, and materials vary.",
    "Results are rounded for readability; add a buffer before ordering, booking, or committing.",
    "Double-check anything with a real cost attached against a local quote."
  ],
  "faq": [
    {
      "q": "Why does exterior paint cover less area than interior paint?",
      "a": "Exterior siding textures like stucco, wood shakes, and embossed vinyl or fiber cement have far more actual surface area per square foot of wall than smooth interior drywall, so more paint is absorbed per square foot of footprint."
    },
    {
      "q": "How many coats does an exterior repaint need?",
      "a": "Two coats is standard for a full color change or a house that hasn't been painted in many years; one coat of maintenance paint can work over sound, similarly-colored existing paint in good condition."
    },
    {
      "q": "Should trim and siding paint be calculated separately?",
      "a": "Yes, trim, fascia, soffits, and shutters are usually a different color and sheen from the field color, so they should be measured and estimated as a separate, much smaller paint quantity."
    },
    {
      "q": "Is it worth buying extra exterior paint for future touch-ups?",
      "a": "Yes, exterior paint fades with UV exposure and batch tinting varies slightly, so keeping a labeled leftover gallon from the original project makes future touch-ups blend in far better than a fresh can years later."
    }
  ],
  "related": [
    "https://www.revenuelab.fyi/toolbox/interior-paint-gallons-calculator",
    "https://www.revenuelab.fyi/toolbox/primer-gallons-calculator",
    "https://www.revenuelab.fyi/toolbox/deck-stain-gallons-calculator"
  ],
  "license": "CC-BY-4.0",
  "citation": "RevenueLab — Exterior Paint Gallons Calculator (https://www.revenuelab.fyi/toolbox/exterior-paint-gallons-calculator)"
}