Calculators
Exterior paint and stain calculators
Siding, trim, fences, decks, garage doors, masonry and roofs, with the extra that rough surfaces drink.
Outside, the can is wrong more often than inside. A gallon that covers 350 square feet on a smooth test panel covers 250 on rough-sawn cedar, 200 on stucco and barely 100 as elastomeric on block, because texture multiplies the real surface and porosity drinks the first coat. Every calculator in this group carries a surface factor you can see and change, so the estimate reflects your wall and not a laboratory panel.
Exterior jobs are also measured differently: a house is a perimeter times a wall height plus gables, a fence is length times height times sides, a deck adds its railings. The calculators take those measurements as you would make them with a tape, and tell you how they were turned into square feet.
10 calculators
Exterior House Paint Calculator
Gallons and pails for a house from its perimeter, storeys, gables, openings and siding type.
Fence Stain & Paint Calculator
Stain or paint for a fence by length, height, sides, style and product, with rough-wood coverage.
Deck Stain Calculator
Deck stain for the boards, railings and steps, by wood condition and product.
Garage Door Paint Calculator
Paint for single, double or custom garage doors by style, with the frame trim.
Exterior Trim, Fascia & Soffit Paint Calculator
Paint for fascia, soffits, rakes, corner boards and the trim around doors and windows.
Stucco & Masonry Paint Calculator
Acrylic masonry paint or elastomeric by texture, with the primer, in gallons and pails.
Metal Railing & Gate Paint Calculator
Rust primer and enamel for iron railings and gates, by openness, in quarts or spray cans.
Roof Coating Calculator
Elastomeric, silicone or aluminium roof coating from the roof area and pitch, in 5-gallon pails.
Porch & Patio Floor Paint Calculator
Floor enamel or anti-slip paint for a porch, patio or steps, with the primer.
Shed & Outbuilding Paint Calculator
Siding and trim paint for a shed, garage or barn from its size, gables, openings and siding.
Guides for this topic
Deck stain coverage: new wood, weathered wood and product type
Deck stain coverage is set by the wood, not the can. A new, smooth deck might take a gallon; the same deck weathered and grey takes two. Here is how to tell which you have.
Planning a fence stain: sides, styles and weather
A 100 ft privacy fence, both sides, is over 1,200 sq ft of rough wood, three and a half times the walls of a 12 × 12 ft bedroom. Here is how to plan the stain, the days and the weather.
Measuring a house exterior for paint
You do not need a ladder to measure a house. A tape round the outside, a count of the storeys and a careful look at the gables give a paint estimate within a can or two.
Siding types and how much more paint rough surfaces take
The same house takes 9 gallons in smooth panels and over 13 in painted brick. Here is where the extra goes, which product each surface needs, and how to plan for it.
Questions people ask
- How much paint does a 2,000 sq ft house need?
- Floor area is a weak guide; the walls are what count. A single-storey house with a 180 ft perimeter and 9 ft walls has about 1,620 sq ft of siding plus gables. On lap siding, which adds about 10% for its profile, two coats at 350 sq ft per gallon come to roughly 10 gallons before trim. The exterior house calculator does it from your perimeter, storeys and gables.
- How much stain does a 100 ft fence take?
- A 6 ft solid fence stained on both sides is 1,200 sq ft. Semi-transparent stain on rough fence boards covers about 200 sq ft per gallon, so one coat is 6 gallons and two coats 12. Staining one side halves it; a picket fence needs about 30% less than a solid one because of the gaps, and a shadowbox about 30% more because the boards overlap on both faces.
- How many coats do exterior jobs need?
- Two coats of topcoat over a sound, primed surface is what the manufacturers specify for their warranties. One coat is enough only when you are refreshing the same colour over paint that is still in good condition. Bare wood, patched areas and chalky old paint need a primer coat first.
- How often does a house need repainting?
- When the film fails, not on a calendar. Wood siding typically goes 5 to 10 years, stucco and fibre cement longer, and the first signs are chalking, cracked caulk and peeling at joints. South and west faces fail first; painting them a few years before the rest is a common way to stretch the full repaint.
- What weather do I need?
- Most latex paints specify air and surface temperatures between 50 and 90 °F (10 to 32 °C), humidity below about 85%, a surface at least 5 °F above the dew point, and no rain for 24 hours after application. Some products are rated down to 35 °F. The data sheet for your paint is the one that counts; the drying time calculator shows how temperature and humidity stretch recoat times.
More calculators on our other sites
Floorings Calculator
How much tile, wood, vinyl, carpet, underlayment and trim a floor needs, and what it costs.
Roofings Calculator
Shingles, pitch, rafters, metal panels, gutters, ventilation and what a new roof costs.
The Woven Garden
Garden and yard calculators for mulch, soil, gravel, sod, pavers, fences and decks.