CP
PAINT CALCULATOR

Barn paint calculator

A small two-story horse barn (24 × 36 ft) has roughly 3,500 sq ft of exterior wall plus about 1,500 sq ft of interior surface and a 900 sq ft roof. Rough sawn siding drinks paint, so coverage drops to around 300–350 sq ft per gallon instead of the 400 you get on smooth walls. The work is mostly about scale and access: two stories, long runs, and a finish you want to last a decade or more before doing it again.

How much paint for a barn

Using the default areas for a typical barn, a two-coat job needs about 7.75 gallons of interior paint (1,500 sq ft of wall) and 20 gallons of exterior paint (3,500 sq ft of siding). Your real numbers will differ — enter your measured areas above and the calculator rounds up to the nearest quart.

In paint alone that's roughly $971–$1943 at $35–$70 a gallon, before primer and supplies. Pick a brand in the result panel for an exact cost.

Barn Red Is Chemistry, Not Just Color

The classic deep red came from farmers mixing linseed oil with iron oxide, basically rust, because it was cheap, on hand, and the iron oxide fought mildew and fungus on bare wood. Modern barn-red acrylics copy that color with synthetic pigments and a proper binder, so they hold their shade and flex far longer than the old oil mix. You get the heritage look without repainting every few years; either path lands at the same iconic red.

Spray The Field, Brush The Trim

A 36-foot, two-story wall by brush is a long weekend; with a rented airless it is closer to an hour of spraying plus back-brushing to push paint into the rough grain. Run the sprayer for the big field walls, then cut in the trim, door frames, and corner boards by brush for a crisp line. Back-brushing the first sprayed coat on rough siding matters: it works paint into the texture instead of bridging over it.

Plan For Height And Access

Two stories means ladders, planks, or a rented scaffold, and gable peaks that need a stable reach. Sort access before paint day, work top down so you are not leaning a ladder against a wet wall, and never spray in gusty wind that throws overspray onto the roof and yard. Tie off on steep ground. The painting is the easy part of a barn; safely reaching the upper third is what turns a one-day job into three.

Prime Bare Wood And The Weak Spots

Old barns have gray, weathered, sometimes punky boards that have to be cleaned and sealed first. Pressure-wash off dirt and loose fibers, let it dry fully, then prime bare and chalky wood with an exterior wood primer so the topcoat does not soak in unevenly. Pay extra attention to the base of walls, end grain, and any board ends near the ground where rot starts. Replace rotten boards before painting; paint never bridges failing wood.

Paint cost by brand

Coverage is similar across the major exterior lines, so the price tier is what moves your bill. Current per-gallon prices for the brands the calculator can price for you:

Brand & linePrice / galCoverage
Backdrop Exterior~$69/gal400 sq ft/gal
Behr Marquee~$52/gal400 sq ft/gal
Behr Ultra~$45/gal400 sq ft/gal
Behr Premium Plus~$33/gal400 sq ft/gal
Benjamin Moore Aura Exterior~$85/gal400 sq ft/gal
Benjamin Moore Regal Exterior~$70/gal400 sq ft/gal
C2 Paint Guard~$65/gal350 sq ft/gal
Diamond Vogel Artistry~$42/gal400 sq ft/gal
Diamond Vogel Palisade~$52/gal400 sq ft/gal
Dunn-Edwards Evershield~$72/gal400 sq ft/gal
Dutch Boy Maxbond Plus~$42/gal375 sq ft/gal
Glidden High Endurance Plus~$28/gal400 sq ft/gal
HGTV Home by Sherwin-Williams WeatherShield~$50/gal375 sq ft/gal
Kompozit ONE~$40/gal388 sq ft/gal
Kompozit PRO~$52/gal388 sq ft/gal
Magnolia Home Exterior~$50/gal400 sq ft/gal
PPG Manor Hall~$55/gal400 sq ft/gal
PPG UltraLast~$48/gal400 sq ft/gal
Rodda Horizon Exterior~$56/gal375 sq ft/gal
Sherwin-Williams Emerald Exterior~$86/gal400 sq ft/gal
Sherwin-Williams Duration~$80/gal400 sq ft/gal
Sherwin-Williams SuperPaint~$60/gal400 sq ft/gal
Sherwin-Williams A-100~$49/gal400 sq ft/gal
Sherwin-Williams Resilience~$73/gal400 sq ft/gal
Valspar Duramax~$50/gal350 sq ft/gal

Frequently asked questions

Why are barns traditionally painted red?+
Practicality, not style. Early farmers sealed bare wood with a homemade mix of linseed oil and iron oxide, the same rust-colored powder that resists mildew and fungus. It was cheap and on hand, so red barns spread across the countryside. The color stuck as tradition even after better paints arrived, and modern barn-red acrylics keep the look while lasting far longer.
What kind of paint should I use on a barn?+
A quality exterior acrylic latex, the same chemistry used on house siding, not a vague "barn paint." It flexes with the wood, resists UV and mildew, and recoats easily. On rough sawn siding plan for it to soak in, so a primer on bare wood and back-brushing the first coat give you even color and the long service life a barn needs.
Should I spray or brush a barn?+
Use both. Rent an airless sprayer for the long field walls, where a two-story run takes about an hour versus a long weekend by brush, then back-brush to drive paint into the rough grain. Brush the trim, corner boards, and door frames for clean lines. Pure spraying on rough siding can bridge the texture and leave thin spots, so the brush still earns its keep.
How do I paint weathered old barn wood?+
Start by pressure-washing off dirt, mildew, and loose gray fibers, then let the wood dry for a few dry days. Scrape flaking old paint, replace any rotten boards, and prime bare and chalky areas with an exterior wood primer so the topcoat bonds instead of soaking in. Old end grain and board ends near the ground need extra primer; that is where failure starts.
How often does a barn need repainting?+
A barn done right with primer on bare wood and two coats of exterior acrylic typically holds up ten to fifteen years, sometimes longer on sheltered walls. Sun-beaten south and west sides chalk and fade first and may need a refresh sooner. Keeping gutters clear, brush cut back, and the base of the walls coated and dry stretches the time between full repaints considerably.
Should I paint the inside of a barn?+
It helps. A coat of light paint or whitewash on interior walls brightens stalls and work areas, reflects light, and seals the wood against moisture and ammonia from livestock. Many owners use a durable, washable exterior or all-surface acrylic inside too. Leave ventilation in mind and avoid sealing green or wet framing; painting damp interior wood traps moisture and invites rot.
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