Estimate paint required and cost in seconds. Enter room dimensions, number of coats and extras (doors, windows) to get a per-room breakdown, charts, CSV export and a sharable link.
Paint Calculator
What is this Paint Calculator?
This Paint Calculator is an interactive tool that estimates the total area to be painted, the volume of paint required (in litres), and the approximate cost. It supports multiple rooms, multiple coats, and deductions for doors and windows. Results include per-room breakdowns, charts and CSV export so you can plan, compare and share.
Why is a Paint Calculator Needed?
Estimating paint manually is error-prone and time-consuming — people often buy too much (waste) or too little (extra trips, delays). This calculator removes guesswork by converting room dimensions into surface area, factoring in real-world deductions and paint coverage ratings to give accurate quantity and cost estimates.
Quick Facts
• One litre of paint usually covers between 250–400 sq ft depending on paint type, porosity and application.
• A standard interior door is roughly 20–22 sq ft; a common window roughly 10–15 sq ft (you can adjust these defaults).
• Two coats are typically recommended for good opacity with most paints.
Real-life Examples
Example 1 — Single bedroom (15′ × 12′ × 9′): Walls = 2×9×(15+12)=486 sq ft. Two coats -> 972 sq ft; at 350 sq ft/L you need 2.78 L per coat set; adjust for doors/windows.
Example 2 — Living/dining open plan with 2 rooms combined: add areas of each room to get totals; use per-room breakdown to buy the right number of litres for each space.
How to Use the Calculator
1. Click “Add Room” and enter each room’s length, width and height (in feet).
2. Select extras: total doors/windows and their average area (or leave default).
3. Choose whether to include ceiling and/or floor.
4. Enter number of coats, paint coverage (sq ft per litre), and cost per litre.
5. Click Calculate Paint Needed — view detailed results, charts and export options.
Why You Should Use This Tool
• Accurate: Uses room geometry and real deductions for windows/doors.
• Efficient: Per-room breakdowns help you prioritize and budget.
• Shareable: Copy a link that pre-fills the form for clients or contractors.
• Portable: Export per-room CSV for estimates and procurement.
Brief History / Context
Calculating paint requirements has long been a practical trade skill. Traditional methods used simple tape-measure arithmetic and rule-of-thumb multipliers. Modern tools combine the maths with product coverage data, reducing waste and cost. This calculator is a digital evolution of those simple rules into an easy-to-use workflow for homeowners and professionals.
Formulas Used (All formulas available)
The calculator uses the following formulas — each measured in square feet (sq ft) unless stated:
Wall area for one room:
Walls = 2 × Height × (Length + Width)
(This assumes 4 walls of a rectangular room, without subtracting openings.)
Ceiling area:
Ceiling = Length × Width
Floor area:
Floor = Length × Width
Total deductions:
Doors area = Number of Doors × Door Area (user input)
Windows area = Number of Windows × Window Area (user input)
Total paintable area:
Paintable = (Walls + Ceilings + Floors – Doors area – Windows area) × Number of Coats
Paint required (litres):
Litres = Paintable ÷ Coverage (sq ft per litre)
Estimated cost:
Cost = Litres × Cost per Litre
Some Tips
• Always round up litres to avoid running out mid-job — paints are sold in whole or set-sized containers.
• Account for surface type (rough surfaces need more paint). If surfaces are rough, reduce the coverage input (e.g., from 350 to 300).
• Use primer recommendations: priming can reduce final paint volume needed, depending on base coat.
• Keep a small overage (5–10%) for touch-ups and absorption differences.
Frequently Asked Questions (FAQ)
Q: Does the calculator include primer?
A: No — this calculator measures paintable area and paint volume. If you plan to prime, include primer separately or adjust the number of coats/coverage accordingly.
Q: Why are my litres low for large areas?
A: Check the coverage value (sq ft per litre). Coverage varies widely; professional coatings may cover more. Also ensure you used correct units (feet).
Q: Can I exclude ceilings or floors?
A: Yes — use the checkboxes to include/exclude ceilings and floors from the calculation.
Q: How accurate is the cost estimate?
A: Cost is a simple multiplication of litres by price per litre. It does not include labour, preparation, masking, or wastage. Use it for material budgeting only.
Disclaimer
The calculations provided are estimates only. Actual material requirements and costs may vary depending on paint brand, surface porosity, application method, and workmanship. Always consult product technical data sheets and consider buying a small extra amount for touch-ups. This tool is offered for convenience and planning purposes and does not replace professional on-site measurement or contractor quotes.