Paint Coverage on Plaster

Painting a 14×18 ft living room with textured/porous walls starts with one honest number: how much paint you actually need. This page works that number out for a 14×18 ft living room with textured/porous walls, using the typical coverage ranges in our paint data — and it starts with a warning worth taking seriously. The result here is an estimate, not a guarantee: coverage and prices vary by brand, finish, surface and region, and the product label on the can you buy governs. A satin paint that covers well on smooth drywall can cover far less on a thirsty or textured surface, and a colour change can add a whole coat. That is why every figure below is shown as a range, and why the calculator on this page asks for your brand, finish and surface instead of handing you a single magic number. Expect about 4–5 gallons for 2 coats here; the rest of this guide shows exactly how that range is worked out, what moves it up or down, and how to measure your own space so you buy the right amount the first time.

Most people planning this job are repainting a room they already live in, which means the walls are in decent shape but the colour is tired or the previous coat has marked. The scenario below matches that case: a straightforward repaint on textured/porous with satin finish, using PPG as the reference brand. Change any one of those — a darker colour, a rougher wall, a cheaper line — and the quantity changes with it. 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 calculator needs six inputs, and each one changes the answer. First, the room dimensions: length times height for each wall, added together — the formula is wall area = 2 × (length + width) × height. For this job that is 2 × (14 + 18) × 9 = 576 sq ft (53.6 sq m) before deductions. Second, the openings to subtract: about 21 sq ft (≈2 sq m) per door and about 15 sq ft (≈1.4 sq m) per window, because you do not paint glass or empty openings. Here that is 2 doors and 3 windows, leaving about 489 sq ft (45.5 sq m) of paintable wall. Third, the number of coats: 2 coats means the paintable area is covered 2 times, so 489 sq ft becomes about 978 sq ft of coverage to buy. Fourth, the finish: satin paint typically covers 200–300 sq ft per gallon (≈18.6–27.9 sq m per 3.79 L) in our data, labelled typical because the can label on your exact product is the authority. Fifth, the surface: textured/porous typically covers 200–300 sq ft per gallon, and the lower of the finish and surface ranges is what limits you in practice. Sixth, the brand: PPG is the reference here, and its own coverage and price ranges are listed in the data file.

The formula is short: gallons = (paintable area × coats) ÷ coverage, run twice — once with the high coverage figure for the low gallon number, and once with the low coverage figure for the high gallon number. That gives you the band. Always round up to whole gallons — paint is sold by the gallon, not by the tenth — and buy a little extra inside that band for 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. Note what the formula leaves out on purpose: it does not assume a single coverage rate. If a retailer quotes you one number for coverage, treat it as a starting point and check the can — the range is the honest figure.

Worked example: a 14×18 ft living room with textured/porous walls

Here is the full arithmetic for a 14×18 ft living room with textured/porous walls, a 14 ft by 18 ft space (4.3 m by 5.5 m) with 9 ft (2.7 m) ceilings.

Step 1 — gross wall area. 2 × (14 + 18) × 9 = 576 sq ft.

Step 2 — deduct the openings. Subtract about 21 sq ft per door (2 × 21 = 42 sq ft) and about 15 sq ft per window (3 × 15 = 45 sq ft). Net paintable area = 576 − 87 = 489 sq ft (45.5 sq m).

Step 3 — multiply by coats. 2 coats × 489 sq ft = 978 sq ft of coverage to buy.

Step 4 — divide by the coverage range. satin paint on textured/porous typically covers 200–300 sq ft per gallon. At the generous end, 978 ÷ 300 = 3.26 gallons; at the thirsty end, 978 ÷ 200 = 4.89 gallons. Rounded up to whole gallons, that is 4–5 gallons — buy 5 gallons to be safe, and keep the receipt for the unopened spare.

Step 5 — the sanity check. If your 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 another 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. Measure twice before you trust the maths: measure each wall at floor level and again higher up, because older rooms are rarely square, and use the larger figure.

Cost guidance

Costs on this page are ranges, labelled typical retail range — check the current shelf price before budgeting. No single national price is quoted, because paint prices vary by brand, product line, region and retailer, and a price that is right in one store can be wrong in the next. For PPG, typical retail 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 — typical retail range, check current shelf price. Premium lines sit at the top of the range and contractor or mid-tier lines lower down. For this job's 3.3–4.9 gallons, paint alone works out to roughly $80–$295 before rollers, tape, drop cloths and primer, which are separate. That spread is wide on purpose: region, product line and promotions move the shelf price more than any national average could capture, so check the price on the day you buy and keep the receipt. Buying all gallons from the same tint run avoids faint shade lines between batches, and comparing brands only makes sense tier to tier — a premium line against a contractor line is not a fair comparison.

Two cost traps catch first-time painters. The first is ordering the low end of the range and then paying a second trip — or a higher per-gallon price — for the one gallon that finishes the job. The second is forgetting the consumables: rollers, brushes, painter's tape, drop cloths and primer together are a meaningful share of a small job's material cost, and a colour change usually needs primer as well. Compare the total, not the per-gallon price, and keep a little paint for future touch-ups; a matching batch is worth far more than the shelf price of that spare gallon later. If you are hiring the work out, labour is usually quoted separately per room or per sq ft and varies by region and by the condition of the walls — a room that needs patching and sanding costs more to paint than a room in good condition, so get the quote against the same room you used for the material count.

What changes the number for a 14×18 ft living room with textured/porous walls

Textured/porous walls change the maths more than any other input: textured/porous typically covers 200–300 sq ft per gallon, against 350–400 sq ft per gallon for smooth drywall. Prime bare or thirsty textured/porous first — a primer coat is cheaper than the extra topcoat the surface would otherwise absorb — and check the can label on the exact product you buy, because coverage varies by product line as well as by surface. Colour is the biggest single lever after surface: a dark colour over a light wall, or a light colour over a dark one, almost always needs an extra coat, and that extra coat is not a rounding error — it is roughly half the paint again. Surface condition is the second lever: patched, sanded or bare areas drink paint, so prime them first rather than paying for topcoat to do a primer's job. Finish is the third: flat and matte finishes hide imperfections but typically cover at the lower end of the range, while glossier finishes cover a little further per gallon but show every bump. Finally, application matters — a roller loads more paint than a brush, a sprayer more still, and a first coat on thirsty drywall always goes further into the wall than the second coat does. None of these change the formula; they change where inside the range you land, which is why the range, not a single number, is the answer.

Step by step: measure, calculate, order

1. Measure twice. 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. Convert inches to decimal feet (6 in = 0.5 ft) before multiplying.

2. Count the openings. Count every door and window in a 14×18 ft living room with textured/porous walls and subtract about 21 sq ft per door and about 15 sq ft per window. Skipping this step is the most common reason people overbuy by a full gallon.

3. Choose the finish and the coats. Pick satin finish, then decide the 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. Use the calculator on this page. Enter the net area, the finish (satin), the surface (textured/porous) and the brand (PPG). The tool returns a range — 4–5 gallons for the example above — and you should plan on the high end.

5. 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. Coverage varies — the can label governs.

6. Order and check the delivery. Order 5 gallons for the example job, all from the same tint run, and check the batch numbers before you start. Keep primer, rollers and tape dry and within their shelf life.

7. Before you start painting. Wash the walls, patch and sand any holes, mask the trim and floor, and stir — do not shake — the paint. Cutting in the edges first, then rolling the field while the cut-in is still wet, avoids lap marks.

Mistakes that waste paint (and money)

  • Skipping the openings: forgetting to subtract doors and windows can add a phantom gallon to a a 14×18 ft living room with textured/porous walls 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 textured/porous: bare, dusty or glossy surfaces drink paint or reject it, and a wash, sand or primer coat is cheaper than the extra paint.
  • Skipping primer on patches: patched spots flash through the topcoat, and the fix is a third coat over the whole wall instead of one primer coat over the patch.

Frequently asked questions

How many gallons of paint do I need for a 14×18 ft living room with textured/porous walls?

For the worked example on this page — about 489 sq ft of paintable wall, 2 coats of satin paint on textured/porous — the answer is 4–5 gallons. The range exists because coverage varies: satin paint typically covers 200–300 sq ft per gallon, and where you land inside that band depends on the colour change, the wall condition and the application method. Measure your own walls and run the same steps to get your range.

Is one coat enough for a 14×18 ft living room with textured/porous walls?

Usually not, unless you are refreshing the same colour on walls that are already in good condition. One coat can look done under a work light and then show thin patches in daylight, especially over a colour change or patched areas. Two coats is the normal plan for a 14×18 ft living room with textured/porous walls, and a dark-to-light change usually needs a primer coat plus two topcoats. Budget for the second coat up front — it is cheaper than a second trip to the store.

How does satin finish change the amount of paint?

Satin paint typically covers 200–300 sq ft per gallon in our data, which is the range used in the worked example. Flatter finishes hide wall imperfections well but tend to sit at the lower end of the coverage range, while glossier finishes cover a little further per gallon but show every bump and patch. Pick the finish for how the room is used — washability and durability matter more than saving a fraction of a gallon — then use its own coverage range, not a generic one.

Does textured/porous need more paint than smooth drywall?

Textured/porous typically covers 200–300 sq ft per gallon, against 350–400 sq ft per gallon for smooth drywall. If your surface is on the thirsty end of that range, prime first: a primer coat seals the surface so the topcoat goes on evenly instead of disappearing into it. The can label on the exact product you buy governs, so check its coverage range against the one used here before you order.

How much will paint cost for a 14×18 ft living room with textured/porous walls?

Paint alone for the example job runs from roughly the low end of the PPG range times 4 gallons to the high end times 5 gallons — a wide band, because typical retail prices per gallon for PPG run about $25–$60 depending on region and product line. That is a typical retail range, so check the current shelf price before budgeting, and remember rollers, tape, drop cloths and primer are on top. Buying the high end of the gallon range is usually the cheaper mistake: leftover paint is useful, a mid-job shortage is not.

Related calculators

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.