Semi-gloss paint calculator?
Figuring out semi-gloss paint calculator 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 2–3 gallons, roughly $50–$180 for paint alone (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 scenario most people have in mind is a farmhouse kitchen repainted around existing tile. The colour is often classic white, the finish is usually semi-gloss, and the surface is smooth drywall — but change any one of those and the quantity changes with it. A dark colour over a light wall, a thirsty surface, or a second coat for even coverage can each push you from the bottom of the range to the top. That is why a calculator that spits out one exact number is misleading: the honest answer is always a band, and this page works in bands from start to finish.
How the calculation works
The BuildCalc 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 wall area. Coats multiply it — two coats means roughly twice the paintable area, before waste. Brand and finish set the coverage range: for semi-gloss finish, typical coverage runs 300–400 sq ft per gallon (≈27.9–37.2 sq m per 3.79 L). Surface matters just as much: smooth drywall typically covers 300–400 sq ft per gallon, while textured or porous surfaces can drop to 200–300 sq ft per gallon and masonry to 150–250 sq ft per gallon. 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).
The formula is simple: wall area = 2 × (length + width) × height, minus openings; then gallons per coat = wall 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.
Worked example: 11×13 ft kitchen with 8 ft ceilings
Take 11×13 ft kitchen with 8 ft ceilings — a farmhouse kitchen repainted around existing tile. The wall area, after subtracting doors and windows, comes to about 346 sq ft (≈32.1 sq m). With semi-gloss paint on smooth drywall, typical coverage is 300–400 sq ft per gallon. For 2 coats the area to cover is about 692 sq ft. At the generous end, 692 ÷ 400 = 1.73 gallons; at the thirsty end, 692 ÷ 300 = 2.31 gallons. Round up to whole gallons — paint is sold by the gallon, not by the tenth — and the answer is 2–3 gallons, roughly $50–$180 for paint alone (typical retail range, check current shelf price). 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. For Behr, typical prices per gallon run about $30–$60 in the Northeast, $30–$55 in the Midwest, $25–$55 in the South and $30–$60 in the West. Widely sold at big-box retailers; premium one-coat lines sit at the top of the range. For this project's 2–3 gallons (or the quart equivalent for trim and doors), that puts paint alone at roughly $50–$180. 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
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.
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.
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.
Enter the numbers in the paint calculator, select your brand, semi-gloss finish and smooth drywall surface, and read the gallon range — not a single number.
Round up to whole gallons, then add one extra quart or gallon for touch-ups, depending on the size of the job.
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.
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 kitchen 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.
Buying gallons from different batches: tint can drift between runs, so a wall finished with two batches can show a faint line in daylight.
Painting unprepared wood or masonry: bare, dusty or glossy surfaces drink paint or reject it, and a wash, sand or primer coat is cheaper than the extra paint.
Storing leftovers badly: a half-empty can skins over and wastes; decant leftovers into a smaller sealed jar, label it with the room and colour, and keep it indoors.
For kitchen work specifically, the surface is the thing people get wrong most often. Smooth drywall behaves differently from the surface in the next room, so a quantity that was right for the bedroom can be wrong for the kitchen. Check the label for your surface, not for a generic wall, and if the surface is textured, porous or previously painted with gloss, plan on the low-coverage end of the range from the start.
Frequently asked questions
What is semi-gloss paint coverage per gallon?
Typical coverage for semi-gloss paint is 300–400 sq ft per gallon (≈27.9–37.2 sq m per 3.79 L), depending on brand and surface. Semi-gloss is durable and moisture-resistant, which is why it is the usual choice for trim, doors, kitchens and bathrooms. Coverage is always a range, never a single number, and the can label for the exact product you buy governs.
How much semi-gloss paint do I need for a kitchen?
For the example kitchen in this guide, about 2–3 gallons for two coats. The range comes from the coverage band 300–400 sq ft per gallon applied to the measured wall area. Measure your own room, subtract doors and windows, and use the calculator to get your own range rather than borrowing this one.
Where is semi-gloss paint the best choice?
Semi-gloss is durable and moisture-resistant, which is why it is the usual choice for trim, doors, kitchens and bathrooms. In practice, semi-gloss is a good default for the walls in this guide's example room, while kitchens, bathrooms and hallways usually benefit from a more washable finish such as satin or semi-gloss. Trim and doors almost always take semi-gloss or gloss instead, because they are touched constantly.
Does semi-gloss paint need more coats than other finishes?
Not usually because of the finish itself — the number of coats depends more on the colour change, the surface and the paint quality. A dark colour over white in semi-gloss may need three coats, while a same-colour refresh in semi-gloss can look fine in two. Matte finishes can show roller marks if the second coat is applied before the first is dry, so follow the drying time on the can.
Can I use semi-gloss paint in a bathroom or kitchen?
You can, but it is not the usual recommendation: semi-gloss is harder to wipe clean and less moisture-resistant than satin or semi-gloss, so steam, splashes and cooking grease show up faster. If you love the look of semi-gloss in a bathroom, choose a semi-gloss line specifically labelled for kitchens and bathrooms, or use semi-gloss on the ceiling and satin on the walls.
Related guides: Start with the paint calculator to run your own numbers; browse the paint hub for the rest of the paint guides; or return to the BuildCalc home page; see also how much paint for a small bedroom; see also fence paint calculator; see also how much paint for a room.
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.