A common planning value is around 350 to 400 square feet per US gallon for one coat, but the product label is the source that matters. Coverage is affected by the coating, surface, roller nap, application method, film thickness, and substrate.
Direct container-size answers
At a label rate of 400 square feet per US gallon, one quart covers 100 square feet, one gallon covers 400 square feet, five gallons covers 2,000 square feet, and one litre covers about 105.7 square feet or 9.8 square metres for one coat. These are conversions of an example label rate, not universal product promises.
Coverage is per coat
If a wall needs two coats, its area consumes coverage twice. A 400 sq ft wall with 400 sq ft/gal coverage needs about two gallons for two coats before contingency, not one. The same rule reduces a five-gallon pail from 2,000 square feet for one coat to 1,000 square feet for two coats.
Porous surfaces use more
Fresh drywall, masonry, repaired areas, and rough texture can absorb more coating. Primer can reduce uneven absorption, but its own coverage also varies.
Primer, exterior, oil, and gloss coverage
Do not assume that primer, exterior paint, oil paint, gloss paint, and interior wall paint share one spread rate. Even products from the same brand can differ by product line, sheen, colour base, and recommended film thickness. Use the exact can label or technical data sheet in the calculator.
Exact volume versus shopping quantity
The formula produces a continuous volume, while stores sell discrete cans. Keep both numbers: exact volume explains the math; rounded containers form the shopping list.
Practical takeaway
Enter the actual label coverage and keep a modest contingency. Product-specific data beats a universal rule of thumb.
Sources and further reading
Related paint guides
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How much does a can of spray paint cover?
Estimate spray-paint cans from label coverage, coats, object geometry, surface texture, and overspray loss.
Do I need one coat or two?
Choose a realistic coat count based on colour change, surface condition, sheen, and product instructions.