Measured, counted and rounded to the can
How much paint will your job really take?
64 free calculators for paint, primer, stain and wallpaper, inside and out, with the time, the cost and the schedule to go with them. Each one shows its formula, its sourced assumptions and the arithmetic beside the answer, and rounds to the cans you can actually buy.
One 12 × 12 ft bedroom
- Wall paint, two coats
- 2.09 gal
- Ceiling paint, two coats
- 3.02 qt
- Trim enamel, two coats
- 0.98 qt
- Labour, one painter
- 14 h 11 min
8 ft walls, one door and one window, smooth surfaces, 350 sq ft per gallon on walls and 400 on ceiling and trim. Change any of it in the calculators.
- 64calculators, each tested against its worked examples
- 27guides on coverage, coats, primer, costs, spraying and wallpaper
- 0sign-ups or saved data: everything runs in your browser
- October 8, 2026when the coverage, drying and cost figures were last checked
Calculators
Interior painting
How much wall, ceiling, trim, door and cabinet paint a room or a whole house takes.
Wall Paint Calculator
Gallons and cans for the walls of a room from its size, openings, coats and coverage.
Ceiling Paint Calculator
Ceiling paint by room size and texture, from smooth to popcorn, rounded to cans.
Trim & Baseboard Paint Calculator
Quarts of trim enamel for baseboards, crown, door and window casings.
Door Paint Calculator
Paint for a set of doors by style, size, sides and coats.
Window Frame & Sash Paint Calculator
Quarts for window frames, casings and sashes by window size and count.
Accent Wall Paint Calculator
Paint, tinted primer and sample pots for one feature wall, with extra coats for dark colours.
Primer Calculator
Primer gallons by surface: new drywall, patches, colour changes, glossy or stained walls.
Whole-House Interior Paint Estimator
Wall, ceiling and trim paint for a whole house from a count of rooms by size, with optional prices.
Kitchen Cabinet Paint Calculator
Primer and enamel for cabinet doors, drawer fronts and face frames, brushed or sprayed.
Stairwell & Tall Wall Paint Calculator
Paint for up to four tall or sloping walls, with a warning when the height needs a scaffold.
Exterior & staining
Siding, trim, fences, decks, garage doors, masonry and roofs, with the extra that rough surfaces drink.
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.
Cost, hiring & time
What the paint costs, what painters charge, how long the job takes and whether to do it yourself.
Paint Cost Calculator
What the paint, primer and supplies cost for a job, with tax, per gallon and per square foot.
Professional Painter Cost Estimator
A low-to-high estimate of what painters charge for rooms, an interior or an exterior, by prep and region.
DIY vs Hire a Painter Calculator
The cash saving from painting it yourself, the hourly value where it breaks even, and a verdict.
Painting Time Calculator
Hours and working days for a job from the areas, the method, the coats, the prep and the crew.
Painting Cost per Square Foot Calculator
Turn a quote into a price per square foot of wall or floor and compare it with published ranges.
Painting Supplies Calculator
An itemised list of rollers, brushes, tape, drop cloths and sundries for the job, with a cost.
Leftover Paint & Touch-Up Planner
What to keep for touch-ups, what to return or give away, and how to store or dispose of the rest.
Coverage & conversions
The arithmetic every other calculator relies on: square footage, coverage rates, coats, cans and units.
Paint Coverage Calculator
Area a quantity of paint covers, or paint for an area, with a texture factor and coats.
Wall Square Footage Calculator
Paintable area of up to six walls and a ceiling, with the openings subtracted, in sq ft and m².
Paint Quantity Converter
Gallons, quarts, pints, fluid ounces, litres and millilitres, converted exactly and rounded to cans.
How Many Coats Calculator
How many coats a colour change takes, whether to prime, and how much extra paint that means.
Spread Rate & Film Thickness Calculator
Theoretical and practical coverage from volume solids and dry film thickness, the way pros spec it.
Paint Thinning Calculator
How much water or thinner to add for a given percentage, and whether it is within the label limit.
Spray vs Roll Paint Usage Calculator
Paint and cost by roller and by airless sprayer for the same job, with the overspray shown.
Can Size Optimizer
The cheapest mix of pails, gallons and quarts (or litre cans) for the paint you need at your prices.
Paint Weight Calculator
What a quantity of paint weighs with its cans, the trips to carry it, or the paint left in a can by weight.
Sample Pot Calculator
How many sample pots to test your colours with proper patches, and what they cost.
Wallpaper
Rolls, paste, borders, peel-and-stick and removal, with pattern repeat and roll sizes done properly.
Wallpaper Roll Calculator
Rolls by drops, with the pattern repeat, the match and US double or European roll sizes.
Wallpaper Paste Calculator
Ready-mixed paste, powder packets or paste-the-wall adhesive for your rolls, plus wall primer.
Wallpaper Cost Calculator
Rolls, paste, primer, removal and installation priced together, per room and per square foot.
Peel-and-Stick Wallpaper Calculator
Rolls or panels of self-adhesive wallpaper for a wall, with the overlap and repeat counted.
Wallpaper Removal Time & Cost Calculator
Hours and cost to strip old wallpaper by type, layers and method, with the wall repair after.
Wallpaper Border Calculator
Spools of border for a room at the ceiling or chair-rail height, with corners and waste.
Floors, wood & specialty
Concrete, epoxy, sealer, wood stain, floor finish, furniture and metal: coverage by surface, not by can.
Concrete & Garage Floor Paint Calculator
Floor paint, one-part epoxy or sealer for concrete, with the etch and primer for bare slabs.
Epoxy Floor Kit Calculator
Two-part epoxy kits, decorative flakes and clear topcoat for a garage or basement floor.
Masonry & Brick Sealer Calculator
Penetrating or film-forming sealer for brick, block, pavers and concrete by porosity and coats.
Wood Stain & Finish Calculator
Stain, conditioner and clear finish for furniture, doors and woodwork, measured as boxes or by area.
Hardwood Floor Finish Calculator
Polyurethane or hardwax oil for a wood floor by finish type and coats, with the sealer coat.
Furniture Paint Calculator
Chalk paint, enamel or spray cans for a dresser, table or cabinet, measured as a box with its doors.
Concrete Block Filler Calculator
Block filler for concrete block walls by texture, in gallons and pails, before the topcoat.
Radiator & Metal Panel Paint Calculator
Heat-resistant paint for panel, column or baseboard radiators, by brush or spray can.
Sprayers, estimating & bidding
Sprayer usage, tip sizes, production rates, drying windows and the maths of a bid.
Airless Sprayer Paint Usage Calculator
Gallons through the gun with overspray and thinning, spraying minutes from the tip flow, and buckets.
Spray Tip Size Calculator
The airless tip number for your material and fan width, its flow, and whether your pump can run it.
Painting Production Rate Calculator
Hours per task from your production rates and the job conditions, with crew days and hours per 100 sq ft.
Painting Bid Builder
A bid from labour, materials, markup, overhead and profit margin, with the price per square foot.
Paint Drying & Recoat Time Calculator
Touch-dry, recoat and cure times by product, adjusted for temperature, humidity and airflow.
Crew & Schedule Calculator
Working days and a finish date from the hours, the crew, recoat waits and the working week.
Markup vs Margin Calculator
Price, markup, margin and profit from any two of them, with the conversion between the two percentages.
Colour, finish & planning
Sheen, mixing, two-tone walls, stripes, paint versus wallpaper and the calendar.
Paint Sheen Selector
The sheen for a room or surface from traffic, moisture, wall condition and what matters most to you.
Paint Mixing Ratio Calculator
How much of each paint to mix for a ratio and a total, or how much to add to what you have.
Two-Tone & Wainscot Wall Paint Calculator
Paint for each colour of a wall split at chair-rail height, with the openings shared out and the tape.
Striped Wall Calculator
Stripe count and true width for a wall, paint for the base and the stripes, and the tape.
Paint vs Wallpaper Cost Comparison
The same room painted and papered, side by side, with materials and optional labour.
Painting Project Planner
Hours, working days, a finish date and a day-by-day room order for a whole-house paint job.
No calculator matches that. Try "wall", "stain", "spray" or "cost", or browse the full list and the guides.
How the estimates work
- Your surfaces become an areaWalls are the perimeter times the height, less standard doors and windows; ceilings are the floor area; trim is counted in linear feet; doors, cabinets and windows are counted and multiplied by standard sizes you can see and change.
- Coverage, coats and allowance become cansThe area is divided by a coverage figure from manufacturers' data sheets, adjusted for texture, multiplied by the coats the colour change needs, given a small allowance, and rounded up to quarts, gallons and 5-gallon pails, or to litre cans in metric.
- The arithmetic is on the pageEvery result has a breakdown and a "Show the arithmetic" panel, so a surprising figure can be traced to the input behind it, and checked against the can, a quote or a painter's estimate.
Most paint calculators divide a floor area by 400 and stop. These count the openings, the texture, the second coat and the primer, round to cans that exist, and keep wall paint, ceiling paint and trim enamel apart because they are different products. Time and cost come from published production rates and dated cost surveys, each labelled as an estimate. Nothing here replaces the data sheet for your product, which is always the authority on its own coverage and drying times.
Questions people ask first
- How much paint do I need for a 12 × 12 ft room?
- With 8 ft walls, one door and one window, the walls are 349 sq ft after the openings. At 350 sq ft per gallon, two coats and a 5% allowance, that is 2.09 gallons: buy two gallons and a quart. The ceiling takes about three quarts more of ceiling paint, so a gallon.
- How much does a gallon of paint cover?
- Interior wall paint labels say 350 to 400 sq ft per gallon per coat on a smooth surface. Plan with 350 on smooth painted walls, about 298 on light texture and about 245 on rough or porous surfaces, because texture and absorption use more paint than the label assumes.
- How many coats of paint do walls need?
- Two for any change of colour, which is what most manufacturers recommend. One coat is enough only to refresh the same colour over sound paint. A big jump, such as white to navy, takes three coats or one coat of tinted primer under two.
- What does it cost to have a room painted?
- Published 2025 cost surveys put interior painting at about $1.50 to $4 per square foot of wall for walls and ceilings. For a 12 × 14 ft room with ceiling and trim, that is roughly $961 to $2,563, depending on prep, region and the painter.
- How long does it take to paint a room?
- A 12 × 12 ft bedroom with ceiling, trim, one door and one window, at two coats, is about 14 hours of work for one painter. With a recoat wait and six hours of painting a day, plan on about four working days. The door and window take longer than the walls.
- How many rolls of wallpaper does a room need?
- Count full-height drops, not area. A 12 × 10 ft room with 8 ft walls, one door and two windows needs 23 drops; with a 21 in pattern repeat, a US double roll gives three, so eight double rolls, or sixteen single rolls in US pricing.
From the guides
How much paint do I need? The complete method
Five steps turn a tape measure and a paint can label into an order that will not run short, and a worked room shows each of them with real numbers.
Paint coverage explained: why 400 sq ft a gallon rarely happens
The coverage on the can is a laboratory number. Here is what eats into it on a real wall, by how much, and which figure to plan with instead.
How many coats of paint you really need
The number of coats changes the order more than any other input. Here are the rules, the reasons behind them, and the cheaper way round a third coat.
What painters charge: per square foot, per room, per hour
Interior painters charge roughly $1.50 to $4 per square foot of wall, according to published cost surveys. Here is what that means for a room or a house, and why quotes for the same job can differ by double.
Painting a room: quantities, order of work and timing
Ceiling, walls, trim, in that order, and about two days of work for a bedroom. Here is the shopping list, the sequence and the hours, worked through for one real-sized room.
Wallpaper roll maths: double rolls, repeats and drop match
Wallpaper is not bought by area. A room is a number of drops, each cut to the pattern, and the rolls are however many it takes to give you that many drops. Here is the arithmetic.
Built to be checked. Every calculator is tested against its own worked examples before it goes up. Coverage and drying figures come from manufacturers' technical data sheets, production rates from contractor estimating references, and prices from dated 2025 cost surveys, all listed on the methodology page and in the reference tables, last reviewed on October 8, 2026. The site is written by its publisher with AI assistance and human review. Found a figure that looks wrong? Tell us.
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