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Paint Calculator: Walls, Ceiling, Doors, Windows & Coats

Plan wall paint and an optional ceiling from room dimensions, exact-or-planning opening allowances, coat count and editable product coverage.

Maintained by Home Measure Lab Editorial TeamUpdated Method & corrections

Answer first

Estimate paint from coated surface area

Estimate paint from the surfaces you intend to coat, the number of coats and the coverage stated for the selected product.

Project measurements

Enter the project measurements and product values that control this quantity.

Quick answer path

Start with the minimum project measurements, then read the result immediately. Open Project / Pro inputs, verified product presets and cost planning only when the job needs more detail.

Paint planning modeQuick uses room dimensions, coats and coverage. Pro adds opening deductions, ceiling details and entered cost.

Visual measurement check

Verify room length, width and wall height

The room-shell preview keeps floor dimensions separate from wall height before doors, windows, coats and optional ceiling coverage are applied. Planning diagram only. Numeric inputs are authoritative; verify field conditions, product instructions and applicable requirements before acting.

Rectangular prism measurement diagramRectangular prism separating long run, width and height or depth. Length: lengthWidth: widthDepth/height: height

Diagram ready. Change a measurement to update this preview.

ft
ft
ft
Quick values
Quick values
sq ft / gal

Project result

Your paint plan

See gross wall area, editable opening deductions, optional ceiling area, coated coverage, calculated paint and whole-container purchase planning.

Planning estimate only. Verify product coverage, package size, supplier specifications and project requirements before purchasing.

Open Project Planner →

Your project history

Use actual-use history as a planning cross-check

Completed projects can become a private reference for future estimates. Home Measure Lab never changes the calculator result automatically.

0 saved records

No matching historical records are saved in this browser yet.

Historical-use reference—Shown only when at least 2 same-unit records exist.
Add a manual historical record

Historical actual use is project-specific evidence, not a universal waste factor, coverage rule or purchase recommendation. Keep product instructions and current project conditions controlling.

Project field workflow

Carry this calculation through the project

Record wall/opening measurements before coverage planning.

v9 workflow
1 · Measure / recordPaint Wall & Opening Measurement Worksheet
2 · CalculateUse this calculator with the field facts you verified.
3 · Save to projectKeep the result with the rest of the browser-local Project Workspace evidence. 4 · Execute / reconcileRecord field checks and actual usage without rewriting the original plan.

Home Measure Lab keeps measurement evidence, calculated plans and field actuals distinguishable. Project links are browser-local unless you explicitly export them.

Field execution geometry

Mark it from one datum, then verify it

Use the execution schedule with the live measurement diagram above. Numeric inputs and calculator results remain authoritative; verify field conditions, product instructions, code and structural requirements before construction or cutting.

Mark-out & execution schedule

    US cost intelligence

    Turn the material plan into a local budget scenario

    Use current supplier and contractor figures from your project. The calculator never invents a local rate or national “live” price.

    Enter a current material subtotal manually when the calculator result does not include priced materials.
    Pre-tax project subtotal$0.00
    Tax$0.00
    Contingency$0.00
    Planning total$0.00
    Materials share0%
    Labor share0%
    Quote − planning totalNot entered
    Open Quote Sanity Check

    Home Measure Lab does not fetch, infer, or publish live local prices in this release. Enter current supplier and contractor figures for the project being evaluated.

    This tool compares user-entered scope and cost components. It does not determine whether a contractor quote is fair, excessive, fraudulent, code-compliant, or complete.

    Methodology

    Formula & assumptions

    Net wall area

    2 × (length + width) × height − door area − window area

    Door and window areas are user-editable instead of hidden fixed deductions.

    Optional ceiling

    length × width × ceiling coats

    Included only when the ceiling option is selected.

    Coated coverage

    net wall area × wall coats + ceiling area × ceiling coats

    Separates measured surface from repeated coats.

    Paint volume

    coated coverage ÷ product coverage

    Use the coverage printed on the paint product for final purchasing.

    How to measure this project

    Measure room length, width and wall height. Count openings and use the editable area-per-door and area-per-window values as quick planning deductions; replace them with measured averages when openings are unusually large. Turn on ceiling coverage only when the ceiling is part of the same paint plan.

    Before you buy materials

    Coverage rates are product and surface dependent. Rough, porous or strongly contrasting surfaces can need more paint than a smooth, previously coated wall. Use manufacturer coverage and a test area when finish quality matters; the calculator rounds the final purchase quantity to practical whole gallons or liters. When a deducted opening contains a door slab that will itself be painted, use Door Paint Calculator for the slab faces and optional edges instead of assuming the wall deduction also covers that finish quantity.

    Reference

    Paint planning inputs that change the result

    InputWhy it mattersPlanning note
    Opening areaReduces wall surfaceMeasure large doors/windows instead of relying on typical allowances.
    CoatsMultiplies coated coveragePrimer is a separate product unless the coating system says otherwise.
    CeilingAdds a second surfaceUse only when ceiling paint is part of this purchase.
    Coverage rateConverts area to volumeUse the product label; texture and application can reduce real coverage.

    US room planning examples

    See how room size and wall height change paintable area

    These are measurement examples, not standard-room assumptions. Enter the real room dimensions and the coverage printed on the paint product you plan to use.

    Gross wall and ceiling area examples

    Room exampleWall heightGross wall areaCeiling area
    10 × 12 ft8 ft352 sq ft120 sq ft
    12 × 12 ft8 ft384 sq ft144 sq ft
    12 × 14 ft9 ft468 sq ft168 sq ft
    14 × 16 ft10 ft600 sq ft224 sq ft

    Coverage sensitivity for 700 coated sq ft

    Entered product coverageCalculated paint before container rounding
    300 sq ft/gal2.33 gal
    350 sq ft/gal2.00 gal
    400 sq ft/gal1.75 gal

    Planning boundaries

    • Coverage is deliberately editable because texture, porosity, color change, application method and product formulation affect real spread rate.
    • Door/window deductions affect wall area only; the optional ceiling is calculated separately.

    Start from a drawing

    Paint Takeoff Studio

    Upload a plan or screenshot, calibrate one known dimension, trace the relevant geometry, and save the measured evidence before returning to this calculator for product-specific planning.

    Open takeoff studio

    Source evidence

    Primary references behind key assumptions

    These references document specific assumptions used or discussed on this page. The exact product label, technical data sheet, project drawings and applicable requirements take priority.

    Sherwin-Williams — Paint Calculator & coverage FAQ

    Supports: Typical gallon coverage and the warning that application method and surface condition can change actual product requirements.

    Boundary: Use the coverage printed for the exact paint being purchased; the reference does not establish one universal coverage value.

    Sherwin-Williams — How Much Paint to Buy

    Supports: Measure coated wall area, subtract large door/window openings, then use the selected product label coverage.

    Boundary: Measurement guidance does not determine coats, primer need or surface-preparation requirements for a specific project.

    Formula & evidence provenance

    Know which part is arithmetic and which part still needs project evidence.

    Method version v13.0. This record does not replace a product label, project drawing, local requirement or professional design decision. See the site-wide method standard →

    Calculation scope

    Estimate paint from the surfaces you intend to coat, the number of coats and the coverage stated for the selected product.

    Boundary

    Doors, windows, ceilings, trim and major unpainted areas should be handled explicitly so they are not silently counted twice.

    Evidence mode

    registered primary/source evidence

    Questions

    Frequently asked questions

    How much area should I subtract for a door or window?

    The default values are planning shortcuts only. Measure the actual openings or use an average based on your project when accuracy matters.

    Does this include ceiling paint?

    Yes when Include ceiling is selected. The ceiling uses room length × width and the entered ceiling coat count.

    Why can real paint use be higher than the calculator?

    Surface porosity, texture, color change, spray or roller technique and product-specific coverage can all change actual consumption.

    What if the door opening is deducted from the wall but the door itself will be painted?

    Keep the jobs separate. Deduct the opening from wall paint when appropriate, then use Door Paint Calculator to measure the slab face or faces and optional edges that receive the door finish.

    Project pack

    Room walls & paint pack

    Reuse room geometry for wall area, drywall takeoff, paint coverage and a room-level shopping plan instead of re-entering the same measurements.

    Drywall CalculatorContinue →Wall Area CalculatorContinue →Drywall CalculatorContinue →Drywall Sheet Layout CalculatorContinue →Drywall Compound CalculatorContinue →Wallpaper CalculatorContinue →
    Embed this calculator on another website

    Use the lightweight Home Measure Lab widget. The embedded tool is noindex and does not add analytics by default; readers can open the full Home Measure Lab calculator for formulas, assumptions and source notes.

    Keep the natural “Powered by Home Measure Lab” attribution inside the widget. Use the built-in brand attribution as provided; no extra link is required.

    Next step

    Keep this project moving

    Follow the measurement into the most useful related reference, calculator or project view.

    Follow the whole jobPaint a Room workflowContinue →Paint the deducted door slabDoor Paint CalculatorContinue →Understand the inputHow to Measure a Room for PaintContinue →Browse this project typeInterior calculatorsContinue →

    Planning guides

    Understand the inputs behind this calculator

    All guides →

    Paint & Walls

    How to Measure a Room for Paint

    A practical room-measuring workflow for wall paint: perimeter, wall height, openings, coats and product coverage without double-counting surfaces.

    Read guide →

    Paint & Walls

    Paint Coverage per Gallon: How to Use the Label

    Understand paint coverage ratings, why a gallon does not cover every surface equally, and how coverage should feed a room paint estimate.

    Read guide →

    Paint & Walls

    How Many Coats of Paint Should You Plan For?

    Learn how coat count changes paint quantity and which project conditions can require more coverage than a one-coat estimate.

    Read guide →

    Paint & Walls

    Paint Waste and Touch-Up Allowance

    Plan paint overage without hiding it inside the room measurement, and understand when leftover paint is useful rather than waste.

    Read guide →

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