Paint Calculator
Estimate gallons of paint needed for a room. Enter dimensions, number of doors/windows, coats, and coverage rate.
Paint Coverage Rate Reference
Coverage varies significantly by paint type. Use these as a starting point and check your specific product label for the manufacturer’s stated rate.
| Paint type | Coverage rate | Typical coats | Notes |
|---|---|---|---|
| Standard interior wall paint | 350–400 sq ft/gallon | 2 | Most latex interior paints |
| Interior primer | 200–300 sq ft/gallon | 1 | More porous, absorbs more paint |
| Ceiling paint | 350–400 sq ft/gallon | 1–2 | Flat finish hides roller marks |
| Exterior paint | 250–350 sq ft/gallon | 2 | Lower coverage due to texture |
| High-hide paint (dark colours) | 300–350 sq ft/gallon | 2+ | Add coat when covering dark colours |
| Trim / semi-gloss | 350–400 sq ft/gallon | 2 | Measured in linear feet for trim |
Painting Tips From the Pros
- →Buy 10% more than you calculate. Paint can be discontinuedand touch-ups later require the same batch. Leftover paint stores well for 2–5 years in a sealed can.
- →Use a roller for walls, brush for edges. Cut in (brush along edges, corners, and trim) first, then fill the main wall area with a roller. Work in 2–3 ft² sections and maintain a wet edge to avoid lap marks.
- →Sand between coats. Lightly sand with 220-grit after the first coat dries (2–4 hours for latex). This removes bumps and improves adhesion for the second coat, giving a smoother finish.
- →Test the colour first. Paint a 30×30cm swatch on the wall and observe it in different lighting (morning, afternoon, artificial light) before buying 10 litres. Paint always looks different on the wall than in a chip book or on screen.
Frequently Asked Questions
How do I calculate how much paint I need?
Add up all wall areas (perimeter × ceiling height), subtract door and window areas, then divide by the paint coverage rate (typically 350 sq ft per gallon). Multiply by the number of coats. This calculator does all of this automatically.
What is a typical paint coverage rate?
Most interior wall paints cover 350–400 square feet per gallon. Primer covers 200–300 sq ft/gallon (more porous surface). Exterior paint covers 250–350 sq ft/gallon. High-hide specialty paints may cover 300–350 sq ft/gallon. Check the label on your specific paint for the manufacturer’s stated coverage.
How many coats of paint do I need?
Going from white to another light colour: 1–2 coats. Going from dark to light (e.g. red to white): 3+ coats, sometimes with primer first. New drywall: primer first, then 2 coats. Same colour touch-up: 1 coat. Bold or deep colours: 2 coats minimum for even coverage.
Should I paint walls or ceiling first?
Always paint the ceiling first, then walls, then trim (skirting boards, window frames, doors). This order lets you overlap slightly onto walls when painting the ceiling, then cover those overlaps when you paint the walls, and finally paint trim last for clean edges.
Do I need to prime before painting?
Prime when: painting new drywall, going from a very dark to a light colour, painting over stains or water marks, or painting bare wood/metal. Skip primer when: repainting with the same or similar colour on a previously painted wall in good condition.
What is the difference between interior and exterior paint?
Interior paints are formulated for low VOC, washability, and colour retention in controlled environments. Exterior paints contain UV inhibitors, mildewcides, and flexible resins to handle temperature swings, rain, and direct sunlight. Never use interior paint outside — it will peel and fade rapidly.
Is this paint calculator free?
Completely free. Enter your room dimensions and get your paint quantity estimate in seconds.
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