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Paint calculator

Estimate how much paint you need for a room — walls, ceiling, or both — with opening deductions for windows and doors and a configurable coverage rate that matches what's actually printed on the can. The math rounds up to whole gallons because paint doesn't come in fractions, and the tool flags counts that look off so you don't end up short.

Estimate

4 gallons

528.0 sq ft · 2 coats · 350 sq ft per gal

Wall area (gross)
384.0 sq ft
Openings deducted
0.0 sq ft
Wall area (net)
384.0 sq ft
Ceiling area
144.0 sq ft
Total area painted
528.0 sq ft
Paint needed (×2 coats)
4 gallons

Estimate rounds up to whole gallons — paint comes in fixed sizes and you'll want a touch-up margin anyway.

Doing tile in the same room?

The free tile calculator draws a scaled diagram with full-tile and cut-tile counts for floors, backsplashes, and shower walls — useful when the paint and tile go up in the same week.

Paint coverage rates by quality

The coverage rate printed on the can isn't the same across the aisle. Premium paint is denser, hides more in one pass, and dries faster between coats — which means the gallon goes further on the wall. The three tiers below cover essentially every interior wall paint sold in the US market in 2026:

TierExamplesPriceCoverageCoatsRecoat
PremiumBenjamin Moore Aura, Sherwin Williams Emerald$45–65 / gal350–400 sq ft / gal1–24 hours
Mid-rangeSW SuperPaint, BM Regal Select, Behr Marquee$30–45 / gal300–350 sq ft / gal24 hours
BudgetBehr Premium Plus, BM Ben$20–30 / gal250–300 sq ft / gal2–32 hours

Two practical notes. First, the “one-coat” claim on Behr Marquee, Benjamin Moore Aura, and Sherwin Williams Emerald is real but conditional — it requires a clean primed surface and a same-color or lighter substrate. Specify two coats on every estimate to keep the budget honest. Second, the coverage rate is for the flat or matte sheen in the line. Eggshell drops 5–10 sq ft per gallon, satin another 5–10, semi-gloss another 10–15. Glossier paint has more resin and less pigment by volume, which is why you can see through it on the first coat.

How much paint do I need for…

Round-number scenarios for the rooms people repaint most often. The numbers assume a mid-range paint (350 sq ft per gallon), two coats, and one or two openings — plug your exact dimensions into the calculator above for a number that matches your room, not a generic one.

ScenarioSurfacesPaint needed
Small bathroom (5×8, 8 ft ceiling)Walls only~1 gallon for 2 coats
Standard bedroom (12×12, 8 ft)Walls + ceiling2–3 gallons
Living room (16×20, 9 ft)Walls + ceiling3–4 gallons
Whole-house interior (1,500 sq ft)Walls + ceilings10–12 gallons

A few patterns worth knowing. Bathrooms almost always come in under a gallon for walls — the small footprint plus a door and a window leaves <200 sq ft of net wall, which one gallon of premium paint covers twice over. Bedrooms hover at the 2-gallon line, and adding the ceiling pushes you over. Living rooms with 9-foot ceilings break 3 gallons because the extra foot of height adds 70+ sq ft per long wall. Whole-house interiors average around 130 sq ft per finished square foot of floor — multiply your square footage by that ratio for a fast sanity check.

Do you need primer?

Four scenarios where the answer is yes, in order of how often they come up. New drywall needs a PVA primer (Zinsser Bulls Eye 1-2-3 or Kilz PVA, $20–30/gal) to seal the paper face so the topcoat doesn't flash and so the second coat doesn't lap-mark. Skipping this on a fresh drywall job is the single most common cause of a blotchy finish.

Dark-to-light color shifts — anything spanning more than 4–5 shades on a paint chip's value scale — need a tinted gray primer. The store will tint Zinsser 1-2-3 to roughly halfway between the existing and target color, which collapses what would be 3–4 coats of topcoat into 2.

Water-stained ceilings or walls need a stain-blocking primer. Latex topcoats don't seal the stain — the brown ring bleeds back through within a week. Kilz Original (oil) is the standard answer; Zinsser BIN (shellac) is faster-drying and better on heavy stains but smells aggressive and demands ammonia for cleanup.

Tannin-rich woods — cedar, redwood, knotty pine — bleed brown through latex. BIN shellac is the only primer that reliably blocks it; oil-based primers slow it down but don't stop it on the worst boards. For spot-priming small patched areas, an aerosol can of Kilz Original or BIN is sufficient.

Sheen choice and where to use it

Six sheens, six different jobs. The defaults below match what most US painters spec when the homeowner says “just pick something normal”:

  • Flat

    Ceilings, formal dining rooms, low-traffic walls. Hides imperfections better than any other sheen — the trade-off is that you can't scrub it without burnishing.

  • Matte

    Modern alternative to flat — same low-reflection look, with enough binder to wipe with a damp cloth. The default pick for living rooms and bedrooms in any premium line.

  • Eggshell

    Slight sheen, washable, the workhorse for most living rooms and bedrooms in mid-range and budget lines. Behr Premium Plus eggshell is the volume default at Home Depot.

  • Satin

    Bathrooms, kitchens, kids' rooms, hallways — anywhere you need to scrub fingerprints and splash without damaging the finish. Mildew-resistant variants (BM Aura Bath & Spa, SW Emerald Interior) are worth the upgrade for showers.

  • Semi-gloss

    Trim, doors, baseboards, window casing. The default trim sheen for most US homes. Pair with a satin or eggshell wall for a subtle contrast; pair with matte for a more obvious one.

  • High-gloss

    Cabinets, accent doors, the occasional statement built-in. Highest reflection, hardest finish, lowest tolerance for prep imperfection — every dent shows. Use a hard enamel (BM Advance, SW Emerald Urethane Trim) and sand between coats.

Sheen also affects how much paint you need. Glossier paints have more resin and less pigment, so they hide less per coat — figure 5–15 sq ft less coverage per gallon as you climb the ladder from matte to high-gloss. The calculator's coverage-rate field lets you dial that in directly.

What affects your paint project cost

Material vs labor split. DIY paint jobs are roughly 80% material and 20% your time. Contractor jobs flip that — about 30% material and 70% labor, which is why the up-charge for premium paint barely moves the total on a hired job but doubles the material line on a DIY job. Spec'ing the better paint when a crew is on-site is almost always worth it.

Prep work. Filling holes (DAP DryDex spot spackle, $7/tub), sanding patches with 120-grit, masking with 1.5" FrogTape ($8/roll), and dropping floors with paper or canvas — for a typical room, expect 2–4 hours of prep before the first coat. Contractors price prep at $1.50–3 per sq ft of wall when the surface is in average condition, more if you've got nail-pop drywall or glossy trim that needs deglossing.

Ceiling repaint markup. Ceilings cost about 30% more per square foot in labor than walls — neck strain, cut-in around fixtures, and the fact that drips land on whatever's below. Most painters quote ceiling work separately ($1.50–4 per sq ft) rather than rolling it into a flat per-square-foot wall rate.

Cut-in labor. The 2-inch band at the ceiling line, corners, and trim edges is where every paint job gets slow. Cut-in is roughly 30–40% of the total painting hours on an average room — the rest is roller fill. Long, straight, obstacle-free walls drop that share; rooms with chair rail, crown molding, multiple windows, and built-ins push it well past 50%.

The seven paint questions that go with this calculator (coverage rates, primer scenarios, how much paint for a bathroom or bedroom, sheen choice, and 2026 paint pricing) are on the main FAQ page so they sit alongside the rest of the product FAQs.

Read the paint FAQs →

Ready to plan the rest of the room?

The free tile calculator draws a scaled diagram with full and cut tile counts for floors, backsplashes, and shower walls — useful when paint and tile both land in the same week. Or jump to pricing to see what a Pro account unlocks.