Quart Benjamin Moore Paint Calculator: How Much to Buy

This calculator estimates how many quarts of Benjamin Moore paint you need for a room, based on the total wall area you enter, the number of coats, and the paint’s coverage rate. You input your wall dimensions (or total square footage), select the surface type, and it returns the required quarts, plus the equivalent gallons and liters. The result is a practical starting point for your shopping list, though you should always round up and account for waste.

Formula

The core formula is straightforward: divide the total paintable area by the coverage rate of one quart, then round up to the nearest whole quart. Benjamin Moore’s standard interior paint covers about 400 square feet per gallon, which means 100 square feet per quart. The formula used here is:

Quarts needed = ceil( (Area × Coats) / (Coverage per quart × Surface factor) )

• Area – total wall area in square feet (or square meters, but you must convert to square feet for this calculator).
• Coats – number of coats you plan to apply (usually 2 for a color change, 1 for same-color touch-up).
• Coverage per quart – 100 sq ft per quart for Benjamin Moore’s typical interior paints (some lines vary).
• Surface factor – 1.0 for smooth drywall, 0.75 for textured surfaces, 0.6 for highly porous surfaces like bare wood or unprimed drywall.

The calculator also converts the quart result to gallons (1 gallon = 4 quarts) and liters (1 quart = 0.946353 liters). For the gallon output, it rounds up to the nearest whole gallon, because paint is sold in full gallons.

Worked Example

Using the default values: a 400 sq ft wall area, 2 coats, smooth surface (factor = 1.0).

1. Total coverage needed = 400 × 2 = 800 sq ft.
2. Divide by coverage per quart: 800 ÷ 100 = 8 quarts.
3. Round up to nearest whole quart: 8 quarts (already whole).
4. Gallons = ceil(8 ÷ 4) = 2 gallons.
5. Liters = 8 × 0.946353 = 7.57 liters.

The calculator shows 8 quarts, 2 gallons, and 7.6 liters. This matches what a painter would buy: two gallon cans, or eight quart cans, for a 400 sq ft room with two coats.

Why Benjamin Moore Coverage Varies

Benjamin Moore’s paint lines have different coverage rates. For example, their Regal Select and Aura lines typically cover 400 sq ft per gallon, but some budget lines or specialty finishes (like high-gloss or primer) may cover less. The 100 sq ft per quart figure is a safe average, but always check the specific can’s label for the exact spread rate. Textured surfaces, such as stucco or knockdown, can reduce coverage by 20–30% because the paint fills the texture. Porous surfaces like raw wood or unprimed drywall absorb more paint, sometimes requiring an extra 50% more paint than smooth drywall.

How to Measure Your Wall Area

To get accurate results, measure each wall’s height and width, then subtract areas for windows and doors. A typical door is about 21 sq ft, and a standard window is about 12 sq ft. For a rectangular room, the formula is:

Wall area = 2 × (length + width) × height – (window area + door area)

If you’re painting a ceiling, measure the floor area (length × width). For trim and baseboards, measure the linear footage and multiply by the width of the trim. This calculator is designed for walls, but you can adapt it by entering the appropriate area.

Common Mistakes and How to Avoid Them

• Forgetting to subtract windows and doors – this can overestimate by 10–15%.
• Using the wrong coverage rate – always check the can; some paints cover 350 sq ft per gallon, not 400.
• Not rounding up – you can’t buy a fraction of a quart, so always round up to the next whole quart.
• Ignoring surface condition – if you’re painting over a dark color or bare drywall, you may need a primer or an extra coat.
• Mixing units – if you measure in meters, convert to square feet (1 m² = 10.764 sq ft) before using the calculator.

Quarts vs. Gallons: Which Should You Buy?

For most rooms, buying gallons is more economical. A gallon of Benjamin Moore interior paint typically costs about the same as four quarts, but you get a slight discount per quart when buying a gallon. For example, if a quart costs $20, a gallon might cost $70, saving you $10. However, quarts are useful for small projects, touch-ups, or when you only need a small amount of a custom color. If your calculation shows 5 quarts, it’s often better to buy 1 gallon and 1 quart (which gives you 5 quarts total) rather than 5 separate quart cans, because you’ll have extra paint for future touch-ups.

Limitations of the Calculator

This calculator provides an estimate, not a guarantee. Real-world coverage depends on application method (roller, brush, or spray), paint thickness, and the skill of the applicator. Spraying typically wastes 10–20% more paint than rolling. Also, if you’re painting a new color over a dark one, you might need three coats instead of two. Always buy 10–15% extra paint to account for waste, spills, and touch-ups. The calculator does not include primer, which is a separate product with its own coverage rate.

Frequently Asked Questions

How many square feet does a quart of Benjamin Moore cover?

A quart of Benjamin Moore interior paint typically covers about 100 square feet per coat, assuming a smooth, primed surface. This is based on the standard 400 sq ft per gallon coverage. Textured or porous surfaces will reduce that coverage, sometimes to 75 sq ft or less per quart.

Is it cheaper to buy a gallon or four quarts?

Usually, a gallon is cheaper per ounce than buying four individual quarts. However, if you only need a small amount for a touch-up, a quart is more practical. For large projects, buying gallons reduces the number of cans and often saves money.

Do I need to prime before painting with Benjamin Moore?

Priming is recommended for bare drywall, wood, or when covering a dark color with a light one. Primer seals the surface and improves adhesion, which can reduce the number of topcoats needed. Benjamin Moore offers specific primers like Fresh Start, but any quality primer works.

How many coats of paint should I apply?

Two coats are standard for a uniform finish and better durability. One coat may suffice if you’re painting the same color or using a high-coverage paint, but two coats ensure even color and hide any imperfections.

What if my wall area is in square meters?

Convert square meters to square feet by multiplying by 10.764. For example, a 20 m² wall is 215.28 sq ft. Enter that number into the calculator to get the quarts needed.

Can I use this calculator for exterior paint?

Yes, but exterior surfaces often require more paint due to texture and weather exposure. Use a lower surface factor (e.g., 0.6 for stucco or wood) and consider an extra coat for durability. Also, exterior paints may have different coverage rates, so check the label.

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in area | Total wall area | sq ft | 400 | 0
in coats | Number of coats | - | 2 | 1
sel surface | Surface type | Smooth=1, Textured=0.75, Porous=0.6
out quarts | Quarts needed | qt | ceil((area * coats) / (surface * 100) / 0.25) | 0
out gallons | Gallons needed | gal | ceil((area * coats) / (surface * 100) / 4) | 0
out liters | Liters needed | L | ((area * coats) / (surface * 100)) * 0.946353 | 1