How many square feet does one gallon of paint cover?

One gallon of quality interior wall paint typically covers approximately 350 to 400 square feet (roughly 33 to 37 square meters) with one coat on a smooth, primed surface.

Should I always apply two coats of paint?

Yes. While premium 'one-coat guarantee' paints exist, two coats provide significantly richer color depth, uniform sheen, and superior scrub resistance against daily wear.

Do I need a separate primer coat?

Primer is necessary when painting over bare drywall, raw wood, glossy surfaces, repaired spackle patches, or when transitioning from a dark paint color to a pale shade.

How do I calculate ceiling paint coverage?

Ceiling square footage equals room length multiplied by room width (Length × Width). A 12 × 15 ft room has 180 sq ft of ceiling, requiring roughly half a gallon for one coat.

What should I do with leftover paint?

Store clean leftover paint in an airtight container in a climate-controlled room for future touch-ups. Never let paint freeze, as freezing irreversibly separates latex emulsions.

DIY & Trades100% Client-Side Local Execution•Updated 2026

Wall Paint Coverage & Gallon / Liter Estimator

Name: Wall Paint Coverage & Gallon/Liter Estimator
Author: AnshuTechy

Calculate net paintable wall surface area, deduct windows and doors, and determine exact gallons or liters of paint and primer needed for your room.Documentation & FAQs ↓

Wall Paint Coverage & Gallon/Liter Estimator — Interactive Console

Runs locally in your browser • Instant output

Measurement System

Room Length (ft)

Room Width (ft)

Ceiling Height (ft)

Doors (Deduct ~21 sq ft each)

Windows (Deduct ~15 sq ft each)

Number of Paint Coats

Include Ceiling in Paint Area Calculation

Paint To Purchase (2 Coats)3 GallonsExact: 2.67 gallons

Net Surface Area468 sq ftDeducted 72 sq ft openings

Primer Needed (1 Coat)2 GallonsRecommended for fresh drywall

Step-by-Step Instructions

4 Steps to Completion

1Phase 1

Enter the room's length, width, and ceiling height.

2Phase 2

Specify the number of doors and windows to deduct cutouts.

3Phase 3

Select the number of paint coats (2 coats recommended for fresh drywall or color changes).

4Phase 4

Review net paintable square footage and exact cans of paint to buy.

Practical Use Cases & Real-World Scenarios

DIY Home Renovation

Estimate paint budget and can counts before visiting Home Depot, Lowe's, or local paint stores.

Contractor Estimates

Provide clients with quick, accurate material cost projections for interior room painting.

Accent Wall Calculations

Calculate paint needed for a single accent wall without buying an unnecessary full gallon.

Related Editorial Guide on AnshuTechy15 Best Painting Tools for Your Next Project in 2026

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Wall Paint Coverage & Gallon / Liter Estimator

Step-by-Step Instructions

Practical Use Cases & Real-World Scenarios

Automatic Window & Door Deductions

Imperial & Metric Units

Multi-Coat & Primer Modeling

Paint Can Rounding Optimizer

Frequently Asked Questions

15 Best Painting Tools for Your Next Project in 2026

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