# Exterior house paint calculator

> 40′ × 25′ house, 2 stories: 2274 sq ft of siding and 439 sq ft of trim take 19.75 gal, paint + primer, and the job needs a 28 ft ladder. Siding, trim, doors and shutters: gallons, primer, caulk and ladders, with lead-safe rules for older homes.

## What to buy (40′ × 25′ house, 2 stories)

Every line shows the quantity to buy and how StudSheet got it: the spacing, the waste and the package size, so you can check it before the supply house or the quote.

| Buy | Material | How StudSheet counts it | What it is for |
|---|---|---|---|
| **3 five-gallon buckets + 1 quart** | Exterior house paint (satin or flat, 2 coats) | 2274 sq ft of wood lap siding (2340 sq ft of wall + 2 gables × 78 sq ft − 222 sq ft of windows and doors) × 2 coats ÷ 300 sq ft/gal = 15.16 gal. 5-gallon buckets cost less per gallon than singles. | 100% acrylic exterior latex for siding; the can lists coverage and the lowest temperature it goes on at. |
| **3 gallons** | Exterior trim and door paint (satin or semi-gloss, 2 coats) | 164 sq ft of window and door trim and corners + 227 sq ft of fascia and soffit + 2 doors (48 sq ft) = 439 sq ft × 2 coats ÷ 350 = 2.51 gal. One color for all of it — split it if the doors get their own. | Satin or semi-gloss exterior acrylic for trim, fascia, soffits, doors and shutters. |
| **1 gallon + 1 quart** | Exterior primer (stain-blocking) (1 coat, scraped spots) | 15% of 2274 sq ft = 341 sq ft scraped to bare ÷ 300 sq ft/gal = 1.14 gal. Stain-blocking, so cedar and redwood don’t bleed through (some say two coats on cedar). | For bare wood and scraped spots; stain-blocking so cedar and redwood tannins don’t bleed through. |
| **1 quart** | Exterior primer (stain-blocking) (1 coat, scraped spots) | 15% of the trim = 59 sq ft ÷ 300 sq ft/gal = 0.2 gal. | For bare wood and scraped spots; stain-blocking so cedar and redwood tannins don’t bleed through. |
| **3 gallons** | House wash concentrate | About one gallon of concentrate per 1000 sq ft (2714 sq ft), mixed as the label says: dirt, chalk and mildew stop paint from sticking. | Cleans dirt, chalk and mildew off siding before paint; mix as the label says (a TSP substitute works too). |
| **3 packs** | Sandpaper, 80 and 120 grit (80 + 120 grit) | Feather the scraped edges so they don’t telegraph through: about a pack per 1000 sq ft of wood — wet-sand by hand if there’s lead. | Feathers scraped edges so they don’t show through the new paint. |
| **1 tub** | Exterior wood filler (quart tub) | Gouges, nail holes and cracked trim joints. | Fills gouges and holes in siding and trim; sandable and paintable outdoors. |
| **9 tubes** | Exterior sealant (paintable) (10.1 oz, paintable) | 488 ft of joints (windows, doors, corner boards and the top of the walls) × 50% that need it ÷ 30 ft per tube at a ¼″ bead. Never seal the drip gaps under siding laps. | Siliconized acrylic or elastomeric sealant rated for outdoors; stays flexible as siding moves. |
| **1 roll** | Painter’s tape 1.41″ × 60 yd | Light fixtures, hardware, and where paint meets brick or stone. | Masks trim and ceilings. |
| **4** | Canvas drop cloth 9×12 (9×12 canvas) | Over plants, walks and the deck below where you’re working; move them along the house. | Doesn’t slide like plastic; reusable. |
| **2 rolls** | Plastic sheeting, 6-mil (6-mil, 10′ × 100′) | Ground cover 10 ft out from every wall you scrape (1700 sq ft), as EPA’s lead-safe rules ask of paid work: chips land on plastic, not in the garden. Fold it up and bag it daily. | Ground cover that catches paint chips under scraping so they can be bagged — lead-safe work needs it. |
| **4 covers** | Roller covers 9″ (½″ nap) | One per product, plus a spare. Rough siding takes a long nap; smooth siding a short one. | Nap length depends on wall texture. |
| **2** | 4″ foam mini-roller | A smooth finish on doors. | Smooth finish on doors and trim. |
| **3** | Tray liners (fits your tray) | One per product. | One per color. |

### In Canada (12.19 m × 7.62 m house, 2 stories)

Set to Canada, the Sheet works the job out again for Ontario: metric sizes, bag sizes, the frost depth and the code notes. It doesn't just convert feet to meters. The first lines:

- **3 × 18.9 L + 1 × 946 mL, Exterior house paint:** 211.3 m² of wood lap siding (217.4 m² of wall + 2 gables × 7.3 m² − 20.6 m² of windows and doors) × 2 coats ÷ 27.9 m² per 3.78 L = 57.4 L. 18.9 L pails cost less per litre than 3.78 L cans. Cans are counted at 3.78 L — read the litres on the can (Canadian “gallon” cans hold 3.6–3.79 L).
- **3 × 3.78 L, Exterior trim and door paint:** 15.2 m² of window and door trim and corners + 21.1 m² of fascia and soffit + 2 doors (4.5 m²) = 40.8 m² × 2 coats ÷ 32.5 m² per 3.78 L = 9.5 L. One color for all of it — split it if the doors get their own.
- **1 × 3.78 L + 1 × 946 mL, Exterior primer (stain-blocking):** 15% of 211.3 m² = 31.7 m² scraped to bare ÷ 27.9 m² per 3.78 L = 4.3 L. Stain-blocking, so cedar and redwood don’t bleed through (some say two coats on cedar).
- **1 × 946 mL, Exterior primer (stain-blocking):** 15% of the trim = 5.4 m² ÷ 27.9 m² per 3.78 L = 0.7 L.
- **3 jugs (3.78 L), House wash concentrate:** About one 3.78 L jug of concentrate per 92.9 m² (252.1 m²), mixed as the label says: dirt, chalk and mildew stop paint from sticking.
- **3 packs, Sandpaper, 80 and 120 grit:** Feather the scraped edges so they don’t telegraph through: about a pack per 92.9 m² of wood — wet-sand by hand if there’s lead.

## The steps, in order

> **PRO STEP: most of it is DIY-friendly; one step needs a licensed pro.** About 75–112 hours of work for this example.

1. Lead check first: test the old paint (lab-tested chips, or a certified inspector) before any scraping or sanding.
2. Wash the house top-down with house wash and a garden hose — no pressure washer on old paint; rinse, then let it dry a day or two.
3. Scrape loose and peeling paint wet, by hand, over the plastic ground cover, feather the edges with sandpaper, and fill gouges and holes with exterior filler.
4. Spot-prime the bare spots, one coat.
5. Seal the gaps with exterior sealant: around windows and doors, along corner boards and trim joints — never the drip gaps under siding laps.
6. Cover plants and walks with drop cloths; take down lights, house numbers and shutters where you can.
7. Soffits and fascia first: they’re the highest, and drips land on unpainted siding.
8. Body: one side of the house at a time, top down, out of direct sun, brushing the laps and rolling the faces; finish whole boards or sections so the edges stay wet. Recoat once the first coat is dry to recoat — see the can.
9. Trim last: window and door trim, doors, brushed and mini-rolled, two coats.
10. Last coat: no rain or dew on it for at least 4 hours (the can says how long). Then pull tape, rehang what you took down, and label a can for touch-ups.

## Tools (21)

Must-have tools first, then the ones that help and the ones to rent for the day.

| Tool | Need | Why |
|---|---|---|
| **Extension ladder (28 ft)** | **Must have** | The highest point is about 24 ft up; a ladder of 28 ft reaches about 27 ft (Werner) |
| **Ladder stabilizer (standoff)** | **Must have** | Holds the ladder off the siding and gutters, and steadies it |
| **Ladder leveler** | Good to have | Levels the ladder on sloped ground and steps |
| **Step ladder (6 ft)** | **Must have** | First-floor trim, doors and soffits |
| **Pump sprayer** | **Must have** | Puts on the house wash |
| **Carbide paint scraper** | **Must have** | Peeling paint off fast |
| **Putty knife** | **Must have** | Filler and loose edges |
| **Sanding sponges** | **Must have** | Feathers the edges |
| **Random orbit sander** | Good to have | Only with a HEPA dust shroud on lead paint — or not at all |
| **Caulk gun** | **Must have** | Dispenses caulk and adhesive. |
| **9″ roller frame** | **Must have** | Holds the roller cover. |
| **Extension pole** | **Must have** | Rolls the high siding from the ladder or the ground |
| **2½″ angled sash brush** | **Must have** | Cutting in and brushing out laps |
| **2″ angled trim brush** | **Must have** | Smaller brush for baseboards and casing. |
| **5-gal bucket + roller grid** | **Must have** | Box the paint: pour every gallon of a color into one bucket and mix |
| **5-in-1 painter’s tool** | **Must have** | Scraper, can opener, roller squeegee — the painter’s pocket knife. |
| **Safety glasses** | **Must have** | Scraping and overhead work |
| **Work gloves** | **Must have** | Tack strip, block and lumber shred hands. |
| **Half-face respirator (P100)** | **Must have** | For any scraping until the lead test is back |
| **Lead-safe work kit** | **Must have** | Sheeting, tape, wipes and bags for the cleanup |
| **HEPA dust extractor** | Good to have | Lead: the daily cleanup and any power tool go through a HEPA vacuum |

## Mistakes and how the math works

### Mistakes that cost a callback or a second trip

- **Painting over dirt, chalk or mildew:** Paint peels off the dust, and mildew grows back through it. Wash, rinse and let it dry first.
- **Painting in the sun or before dew:** Paint flashes, laps and blisters in direct sun; late-day dew leaves streaks and surfactant drips. Follow the shade.
- **Sealing the drip gaps:** Caulking the bottom edges of lap siding traps water behind it. Seal joints at trim, not the laps.
- **Dry-scraping or power-washing old paint:** It spreads lead dust and chips into the soil where kids play. Test first, then work wet over plastic.

### What the calculator assumes

- House: 40′ × 25′, 18′ from the ground to the eaves (about 9 ft a story).
- Coverage per gallon per coat: 300 sq ft on wood lap siding (rough and porous surfaces take more; labels range 250–400 on smooth siding), trim 350, primer 300.
- Openings: 15 sq ft a window, 21 sq ft a door, 63 sq ft or 112 sq ft a garage door. Trim: about 8 sq ft a window and 7 sq ft a door of casing; corner boards about 9″ of paint wide, top to bottom; fascia about 8″.
- Gables: half the width × the rise (6/12). Spot-priming covers 15% of the area on a scrape job; spraying uses about 25% more paint.
- Sealant: about 30 ft of ¼″ bead per 10.1 oz tube; half the joints need it.
- Ladders by Werner’s reach heights (24 ft reaches about 23 ft, 28 ft about 27 ft, 32 ft about 31 ft); higher than that, a lift or scaffolding.
- Lead: EPA’s RRP rule applies to paid work on pre-1978 homes, and to rentals. Outside, paid work that disturbs more than 20 sq ft of paint is covered.

## Code, permits and safety

The Sheet sets its code notes for the job's state or province. These are New Jersey's and Ontario's; the [code reference](https://studsheet.com/codes) has more. Always confirm with your building department.

- **High walls: ladder work:** The highest point is about 24 ft up, for a ladder of 28 ft — the riskiest part of the job. Set it 1 out for every 4 up on firm, level ground with a standoff, keep your belt buckle between the rails, and stay well clear of power lines. Many people hire out just the high walls and gables.
- **Find out when the house was built:** Homes built before 1978 may have lead paint, and outside paint often had the most. Test before you scrape or sand (a lab test of chips, or a certified inspector). If lead is present: mist and scrape by hand, no power sanding without a HEPA shroud, no open flame, no heat gun at 1,100°F or more, and no pressure washer; plastic on the ground 10 ft out from the wall, windows and doors closed within 20 ft, chips bagged every day, kids and pets away. EPA’s RRP rule doesn’t cover owners working on their own home, but anyone you pay must be an EPA lead-safe certified firm — for outside work that disturbs more than 20 sq ft of paint — and rentals are covered.
- **Paint weather:** Most exterior latex goes on from about 35–50°F up to 90°F, air and wall both, and needs those temperatures for at least 4 hours after (Behr’s exterior paints say 35–90°F; many paints need 50°F) — read the can. No rain or heavy dew on the way; paint the shady side and follow the sun around the house.

## Questions

### What materials do I need to paint the outside of a house?

For the worked example, a 40′ × 25′ house, 2 stories, the Sheet counts 14 lines with waste included, starting with exterior house paint (3 five-gallon buckets + 1 quart), exterior trim and door paint (3 gallons), exterior primer (stain-blocking) (1 gallon + 1 quart), exterior primer (stain-blocking) (1 quart). Each line's math is in the table above. Put in your own sizes in the [exterior paint calculator](https://app.studsheet.com/p/extpaint) and every line is counted again.

### How long does it take to paint the outside of a house, and can I do it myself?

About 75 to 112 hours for the worked example, in 10 steps. StudSheet stamps it **PRO STEP**: dIY with a pro for one step.

### What tools do I need to paint the outside of a house?

21 in all. The must-haves start with extension ladder (28 ft), ladder stabilizer (standoff), step ladder (6 ft), pump sprayer, carbide paint scraper, putty knife. On the Sheet you mark each one as owned, to buy or to rent.

## Ask about it

Stuck while you paint the outside of a house? Ask in the [Exterior painting group](https://studsheet.com/forum/exterior-painting) of the StudSheet community with this Sheet attached. Homeowners who've done it and verified pros answer, and anyone can read it.

## More painting Sheets

- **[Painting for contractors](https://studsheet.com/trades/painting)**: run this takeoff at your own prices, send the estimate, and get it signed and the deposit paid.
- **[Paint a room](https://studsheet.com/sheets/paint)** (14′ × 12′ room): Prep, primer, paint and supplies — walls, ceiling, trim and doors.
- **[Paint kitchen cabinets](https://studsheet.com/sheets/cabinets)** (20 doors, 8 drawers): Doors, drawer fronts and boxes counted into square feet: degreaser, sanding, bonding primer, cabinet enamel, rollers or a sprayer, and the days it takes.
- **[Stain or seal a deck or fence](https://studsheet.com/sheets/stain)** (16′ × 12′ deck): Cleaner, brightener or stripper, stain or sealer by the gallon for your deck, railings, stairs and fence — first and second coats counted the way the cans say.
- **[All 45 Sheets](https://studsheet.com/sheets)**, across 16 trades.
- **[Code reference](https://studsheet.com/codes):** frost depths, guard heights, stairs, retaining walls.