# Paint calculator

> 14′ × 12′ room, 2 coats: 365 sq ft of wall after the doors and windows, 2.25 gallons of paint in all. Prep, primer, paint and supplies — walls, ceiling, trim and doors.

## What to buy (14′ × 12′ room)

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 |
|---|---|---|---|
| **2 gallons + 1 quart** | Wall paint (eggshell, 2 coats) | 365 sq ft of wall (416 minus 1 doors × 21 and 2 windows × 15) × 2 coats ÷ 350 sq ft/gal = 2.09 gal. | Interior latex. |
| **1 roll** | Painter’s tape 1.41″ × 60 yd | 148 ft to mask (the ceiling line, baseboards and casing) + 10%; 180 ft per roll. | Masks trim and ceilings. |
| **2** | Canvas drop cloth 9×12 (9×12 canvas) | Work one wall at a time and leapfrog them. | Doesn’t slide like plastic; reusable. |
| **1 pack** | Plastic sheeting 9×12 | Cover furniture you can’t move out. | Covers furniture. |
| **1 tub** | Lightweight spackle (8 oz) | Nail holes and dings. | Fills nail holes and dings; sands easily. |
| **2 covers** | Roller covers 9″ (⅜″ nap) | ⅜″ nap for smooth walls — one per product, plus a spare. | Nap length depends on wall texture. |
| **1** | Tray liners (fits your tray) | One per product. | One per color. |

### In Canada (4.27 m × 3.66 m room)

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:

- **2 × 3.78 L + 1 × 946 mL, Wall paint:** 33.9 m² of wall (38.6 minus 1 doors × 2.0 and 2 windows × 1.4) × 2 coats ÷ 32.5 m² per 3.78 L = 7.9 L. Cans are counted at 3.78 L — read the litres on the can (Canadian “gallon” cans hold 3.6–3.79 L).
- **1 roll, Painter’s tape 36 mm × 55 m:** 45.11 m to mask (the ceiling line, baseboards and casing) + 10%; 55 m per roll.
- **2, Canvas drop cloth 2.7 × 3.7 m:** Work one wall at a time and leapfrog them.
- **1 pack, Plastic sheeting 2.7 × 3.7 m:** Cover furniture you can’t move out.
- **1 tub, Lightweight spackle:** Nail holes and dings.
- **2 covers, Roller covers 230 mm:** 10 mm nap for smooth walls — one per product, plus a spare.

## The steps, in order

> **DIY OK: you can do this yourself with standard tools.** About 6–9 hours of work for this example.

1. Clear the room, cover the floor, take off outlet and switch plates.
2. Patch holes; sand smooth when dry.
3. Tape the edges you don’t want painted.
4. No primer needed — spot-prime patches only.
5. Box the paint: pour every gallon of a color into one bucket and mix, so the color doesn’t shift between walls.
6. Cut in along the ceiling and corners with the angled brush.
7. Roll walls top to bottom in 3×3 ft sections, keeping a wet edge. Second coat once the first is dry to recoat (see the can).
8. Pull tape at a 45° angle while paint is slightly soft.
9. Put the plates back. Label a leftover can for touch-ups.

## Tools (14)

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

| Tool | Need | Why |
|---|---|---|
| **9″ roller frame** | **Must have** | Holds the roller cover. |
| **Extension pole** | **Must have** | Rolls walls from the floor and ceilings without a ladder. |
| **2½″ angled sash brush** | **Must have** | Cuts clean lines at ceilings and corners. |
| **5-gal bucket + roller grid** | **Must have** | Two or more gallons of one color: skip the tray |
| **Step ladder (6 ft)** | **Must have** | Reaches 8-ft ceilings safely. |
| **Putty knife** | **Must have** | Fills nail holes and dents. |
| **5-in-1 painter’s tool** | **Must have** | Scraper, can opener, roller squeegee — the painter’s pocket knife. |
| **Sanding sponges** | **Must have** | Low-dust sanding for mud, patches and scuffing old paint. |
| **Screwdriver set** | **Must have** | Outlet and switch covers come off |
| **Safety glasses** | **Must have** | Every cut, every nail, every time. |
| **Work light** | Good to have | Raking light shows holes and roller marks |
| **Paint edger pad** | Good to have | Only if cutting in by hand scares you |
| **Pole sander** | Good to have | Sands high and wide areas from the floor. |
| **Paint tray** | Good to have | For cutting in |

## Mistakes and how the math works

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

- **Skipping primer when it’s needed:** On new drywall or a big color change you get blotchy “flashing” and one or two extra coats.
- **Not boxing the paint:** Two gallons of the “same” color can differ. Mix them together before you start.
- **Wrong nap, overloaded roller:** Drips and texture that doesn’t match. ⅜″ for smooth walls, ½″ light texture, ¾″ heavy.

### What the calculator assumes

- Coverage 350 sq ft per gallon per coat for walls, ceilings and trim (manufacturer ranges run 250–450); primer 300 sq ft per gallon (PVA primers list 300–400).
- Deductions: 21 sq ft per door, 15 sq ft per window.
- Texture uses more paint: +10% light, +25% heavy.
- Trim: 4″ baseboard, 3″ casing; door slabs both sides +15% for edges and panels.
- Buying: a 5-gallon bucket once you’d buy 4+ gallons of one color; quarts under ½ gallon, and a quart instead of another gallon when you need ¼ gallon or less over whole gallons.
- Lead: EPA’s RRP rule applies to paid work on pre-1978 homes, and to rentals.

## 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.

- **Permits:** a job like this usually needs none, but towns set their own rules. Ask your building department if you're not sure.

## Questions

### What materials do I need to paint a room?

For the worked example, a 14′ × 12′ room, the Sheet counts 7 lines with waste included, starting with wall paint (2 gallons + 1 quart), painter’s tape 1.41″ × 60 yd (1 roll), canvas drop cloth 9×12 (2), plastic sheeting 9×12 (1 pack). Each line's math is in the table above. Put in your own sizes in the [paint a room calculator](https://app.studsheet.com/p/paint) and every line is counted again.

### How long does it take to paint a room, and can I do it myself?

About 6 to 9 hours for the worked example, in 9 steps. StudSheet stamps it **DIY OK**: you can do this.

### What tools do I need to paint a room?

14 in all. The must-haves start with 9″ roller frame, extension pole, 2½″ angled sash brush, 5-gal bucket + roller grid, step ladder (6 ft), putty knife. On the Sheet you mark each one as owned, to buy or to rent.

## Ask about it

Stuck while you paint a room? Ask in the [Interior painting group](https://studsheet.com/forum/interior-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 the outside of a house](https://studsheet.com/sheets/extpaint)** (40′ × 25′ house, 2 stories): Siding, trim, doors and shutters: gallons, primer, caulk and ladders, with lead-safe rules for older homes.
- **[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.