How much satin paint for a exterior

Figuring out how much satin paint for a exterior starts with one honest warning: any number you see here is an estimate, not a promise. Paint coverage and prices vary by brand, finish, surface and region, and the product label on the can you actually buy governs. That is the whole point of the BuildCalc approach — every result on this page is a range, so you can plan for the low end and the high end instead of being surprised at the till. In short, expect 1.1–1.3 gallons, so buy 2 gallons for paint alone, roughly $25–$120 (typical retail range, check current shelf price). The rest of this guide shows exactly how that range is worked out, what changes it, and how to measure your own space so you buy the right amount the first time.

The job most people have in mind is a 36 ft run of satin exterior wall, 8 ft high: Exterior paint has the hardest job on the house: sun, rain, frost and temperature swings all attack the film, so the surface is usually wood siding, stucco or masonry, and preparation — washing, scraping loose paint and priming bare spots — matters at least as much as the paint itself. For satin finish, expect the paint to behave as the finish always does — a mid-level sheen that is washable and durable without looking shiny. It is the usual default for busy family rooms, kitchens and hallways. Change any one of those details — the finish, the surface, the number of coats — and the quantity changes with it, which is why this page works in ranges from start to finish.

How the calculation works

The BuildCalc exterior paint calculator asks for the inputs that actually move the answer: room dimensions, number of coats, brand, finish and surface, plus the doors and windows to subtract. Each one matters for a different reason. Dimensions set the paintable area. Coats multiply it — two coats means roughly twice the paintable area, before waste. Brand and finish set the coverage range, and surface matters just as much: a gallon goes much further on sealed drywall than on bare masonry. Doors and windows are subtracted because you do not paint glass or empty openings — a standard door is about 21 sq ft (≈2 sq m) and a typical window about 15 sq ft (≈1.4 sq m).

Coverage is where the range comes from. For satin finish, typical coverage runs 300–400 sq ft per gallon (27.9–37.2 sq m per 3.79 L), and on wood siding the surface range is 250–350 sq ft per gallon. The two ranges overlap at 300–350 sq ft per gallon, which is the planning range used in the worked example below. On masonry or stucco the same paint may cover only 150–250 sq ft per gallon, so check the surface before you trust the high end.

The formula is simple: paintable area = 2 × (length + width) × height, minus openings; then gallons per coat = paintable area ÷ coverage; then multiply by the number of coats and round up. Because coverage is a range, you run the formula twice — once with the high coverage number for the low gallon figure, and once with the low coverage number for the high gallon figure. That gives you the band. Buying a little extra inside that band covers touch-ups, roller absorption and the last half-wall that always seems to appear. One US gallon is 3.79 litres, and one square foot is about 0.093 square metres, so the metric equivalents in parentheses are approximate by design.

Exterior paint has the hardest job on the house: sun, rain, frost and temperature swings all attack the film, so the surface is usually wood siding, stucco or masonry, and preparation — washing, scraping loose paint and priming bare spots — matters at least as much as the paint itself.

Worked example: 36 ft of satin exterior wall, 8 ft high

Here is the full arithmetic for a 36 ft run of satin exterior wall, 8 ft high, worked step by step so you can check every number.

Step 1. Gross wall area: 36 ft × 8 ft = 288 sq ft.

Step 2. Deduct openings: 5 windows at about 15 sq ft each and 1 door at about 21 sq ft — 96 sq ft in total. Net area = 288 − 96 = 192 sq ft (17.8 sq m).

Step 3. Two coats means covering 192 × 2 = 384 sq ft in total.

Step 4. Low end (generous coverage): 384 ÷ 350 = 1.10 gallons. High end (thirsty coverage): 384 ÷ 300 = 1.28 gallons.

Step 5. Round up to whole gallons — paint is sold by the gallon, not by the tenth — and the answer is 1.1–1.3 gallons, so buy 2 gallons for paint alone, roughly $25–$120 (typical retail range, check current shelf price).

If your space is bigger, the same steps scale: measure again, deduct again, apply the same coverage range, and round up again. A space twice this size needs roughly twice the paint, but the coverage range stays tied to the brand, finish and surface, not to the room size. If the walls are a deep colour going over white, or white going over a deep colour, expect to land at the top of the range or add a third coat; a same-colour refresh in good light often lands near the bottom. Either way, the range is the plan: buy the low end and you risk a mid-wall trip to the store, buy the high end and you have touch-up paint for the next few years.

One more check before you trust the maths: measure twice. Measure each wall at floor level and again at picture-rail height, because older rooms are rarely square, and use the larger figure. Count every door and window, and subtract them — skipping that step is the most common reason people overbuy by a full gallon. Then run the same numbers through the calculator with your exact brand and finish selected, and compare: if the calculator's range and this worked example disagree wildly, re-measure before you re-shop.

What it costs (typical retail ranges)

Paint prices are always ranges on BuildCalc, labelled typical retail range — check current shelf price — because the same gallon can cost very different amounts by region and product line. Across the five brands in our data file — Sherwin-Williams, Benjamin Moore, Behr, Valspar and PPG — typical retail ranges run $25–$90 per gallon depending on brand, product line and region. Behr typically runs $25–$60 per gallon and Valspar $25–$55, while Sherwin-Williams typically runs $45–$90 and Benjamin Moore $45–$85, with PPG typically at $25–$60. Check the current shelf price before budgeting — promotions move prices more than regions do, and a sale weekend can shift a gallon by a quarter of its price. For this project's 1.1–1.3 gallons, so buy 2 gallons, that puts paint alone at roughly $25–$120. That figure is paint only: rollers, brushes, painter's tape, drop cloths, primer and a tray typically add a further modest amount, and hiring a painter is a separate cost entirely. If you are comparing brands, compare the same product tier — a premium line against a contractor line is not a fair fight — and remember that a paint that covers in two coats can be cheaper per finished wall than a cheap paint that needs three.

Regional differences are real but modest for most brands: the South and Midwest usually sit a little lower in the range, the Northeast and West a little higher. Promotions move prices more than regions do — a sale weekend can shift a gallon by a quarter of its price — which is another reason no single national price appears anywhere on this site. Check the shelf price on the day you buy, keep the receipt, and buy all your gallons from the same batch or tint run where possible, because even the same colour code can vary slightly between batches.

How to measure and use the calculator, step by step

  1. Measure each wall's length and the ceiling height with a tape measure, in feet and inches, and write every figure down before you do any maths.

  2. Multiply length by height for each wall, add the walls together, then subtract about 21 sq ft per door and 15 sq ft per window.

  3. Choose your coats: one coat only works for a same-colour refresh in good condition; two coats is the normal plan, and a colour change or bare surface usually needs a primer coat plus two topcoats.

  4. Enter the numbers in the exterior paint calculator, select your brand, finish and surface, and read the gallon range — not a single number.

  5. Round up to whole gallons, then add one extra quart or gallon for touch-ups, depending on the size of the job.

  6. Check the can label in the store: confirm the coverage range printed on the exact product matches the range you planned with, and adjust if it does not.

  7. Buy primer separately if the surface is bare, stained or patched — primer has its own, lower coverage range, so do not assume one gallon of primer covers what one gallon of topcoat covers.

Mistakes that waste paint (and money)

  • Skipping the openings: forgetting to subtract doors and windows can add a phantom gallon to a wood siding job.

  • Trusting a single coverage number: coverage is a range, and planning on the best-case figure is how you end up back at the store mid-wall.

  • One coat over a colour change: dark-to-light almost always needs two coats plus primer, and budgeting for one is the classic underestimate on wood siding.

  • Buying gallons from different batches: tint can drift between runs, so a surface finished with two batches can show a faint line in daylight.

  • Painting unprepared wood siding: bare, dusty or glossy surfaces drink paint or reject it, and a wash, sand or primer coat is cheaper than the extra paint.

Frequently asked questions

How many coats of satin paint does wood siding need?

Two coats is the normal plan for wood siding: the first coat seals and evens the surface, the second gives the even colour and the durability. A same-colour refresh in good condition can sometimes look fine in one coat, but a colour change, bare wood or a patched surface usually needs a primer coat plus two topcoats.

What coverage can I expect from satin paint on wood siding?

Typical coverage is 300–350 sq ft per gallon for one coat in typical conditions, from our material data. On a thirstier or rougher patch of wood siding expect the low end of the range; on a smooth, previously painted stretch expect the high end. The can label on the exact product you buy governs — check it before you order.

Can I use satin paint over old paint on wood siding?

Yes, if the old paint is sound: wash the surface, sand glossy spots lightly, and spot-prime bare patches. If the old paint is peeling, flaking or chalky, scrape and prime first — new paint over a failing surface fails with it. A colour change over a dark base usually needs an extra coat whatever the finish.

How do I measure wood siding for paint?

Measure each wall of the house separately, in feet, and subtract about 15 sq ft per window and 21 sq ft per door. Work in feet, convert inches to decimal feet before multiplying (6 in = 0.5 ft), and write every figure down before doing any maths. Measure twice — rooms and fences are rarely as square as they look.

Does satin paint need primer on wood siding?

On bare, patched or stained wood siding, yes: primer seals the surface so the topcoat covers evenly, and primer has its own, lower coverage range, so do not assume one gallon of primer covers what one gallon of topcoat covers. On previously painted wood siding in good condition, a primer coat is usually unnecessary unless you are changing colour dramatically.

Related guides

Results are estimates — verify with the product label. Coverage, pack sizes, yields and prices vary by brand, product line, surface and region; the label on the product you buy governs. Cost figures are typical retail ranges — check the current shelf price before budgeting. Coverage varies — the can label governs.