MovePik

Paint calculator for whole rooms

Measure the room once and get the cans to buy per color, what is left over and a shopping list.

Project name, saving and backup ↓

Measure each room once. Every material on this page is planned from these measurements.

Units

Changing a unit only changes how values are shown. Your measurements stay exactly as entered.

Feet and inches: type 12' 6", 12 6 (= 12 ft 6 in) or 12.5 (decimal feet). Inches alone: 30".

Rooms

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What this planner works out

The planner turns your room measurements and the numbers on the paint label into a shopping quantity: how much paint each color needs, how many cans of the size you choose, and how much will be left in the last can. You can add several rooms, paint the walls and the ceiling in different colors, and add a primer as its own line.

What it doesn’t cover: the condition of your walls (filling, sanding, stain blockers, specialist coatings, damp) or structural and safety questions. The result is only as good as the measurements and the coverage figure you enter.

How to measure

You need the length of each wall (or the room’s length and width), the wall height, and the width and height of each door and window you will not paint. Measure to the nearest half inch or centimeter; the allowance covers the rest. The guide how to measure a room shows the order and how to handle L-shaped rooms.

The method in plain words

  1. Wall area. Perimeter × wall height gives the gross wall area. Subtract the area of every opening to get the net area you will paint. A ceiling uses the floor area.
  2. Paint for each surface. Net area × number of coats ÷ coverage per coat. The coverage (also called the spreading rate) is the area one gallon or one liter covers, printed on the label; it is always per coat, so two coats need twice the paint.
  3. Add up the same paint. Every room and surface you assign to the same paint entry is added together. If you enter the same paint twice, the planner flags it so you can merge the two entries. Different colors are kept apart, and primer is a separate material with its own coverage.
  4. Add the extra for touch-ups (the allowance). A percentage on top for rollers, trays, touch-ups and rough surfaces. 10% is a common starting point; you can change it.
  5. Round up to whole cans. Divide by the can size and round up, never down. The difference is your leftover.

Painting a door, stair treads and risers or a chimney breast as well? Add them under Painted areas in step 1; openings are never taken off those. For the outside walls of a house, with gables, use the exterior paint calculator. Planning decorator’s caulk for gaps before you paint? In step 2, open Plan other materials and add it under Sealant and filler.

Worked example in meters and liters

A room 4 m × 3 m with 2.5 m walls, a door and a window that together measure 3 m², two coats of a paint whose label says 10 m² per liter per coat, 10% allowance and 2.5 L cans:

  • Perimeter: 2 × (4 + 3) = 14 m
  • Gross wall area: 14 × 2.5 = 35 m²
  • Net wall area: 35 − 3 = 32 m²
  • Paint for two coats: 32 × 2 ÷ 10 = 6.4 L
  • With 10% allowance: 6.4 × 1.1 = 7.04 L
  • Cans: 7.04 ÷ 2.5 = 2.816, rounded up to 3 cans (7.5 L)
  • Left over: 7.5 − 7.04 = about 0.46 L

Worked example in feet and gallons

A room 12 × 10 ft with 8 ft walls, one 32 × 80 in door and one 36 × 48 in window. The label coverage used here is an example of 350 sq ft per gallon per coat; use the number on your own can. Two coats, 10% allowance, one-gallon cans:

  • Perimeter: 2 × (12 + 10) = 44 ft
  • Gross wall area: 44 × 8 = 352 sq ft
  • Door: 32 × 80 = 2,560 sq in ÷ 144 = 17.78 sq ft
  • Window: 36 × 48 = 1,728 sq in ÷ 144 = 12 sq ft
  • Net wall area: 352 − 17.78 − 12 = 322.22 sq ft
  • Paint for two coats: 322.22 × 2 ÷ 350 = 1.841 gal
  • With 10% allowance: 1.841 × 1.1 = about 2.03 gal (2.025)
  • Cans: 2.025 rounded up gives 3 one-gallon cans, with about 0.97 gal left over

Without the allowance, 2 gallons would only just cover it, with no margin for the roller and tray.

If your gallon of tinted paint holds less than 128 fl oz, enter the real fill as the can size. The guide on paint coverage and coats explains why, and how pack rounding works covers the rounding step in more detail.

Before you start: old paint

In the United States, homes built before 1978 may have lead-based paint. Sanding, scraping or heat-stripping it can release lead dust. Read the EPA’s lead-safe renovation guidance for do-it-yourselfers before preparing the surface. In Great Britain, see the HSE lead pages. In other countries the dates and rules differ, so check your national guidance.

If you are also replacing the floor, the room refresh planner uses the same measurements for paint and flooring.

Frequently asked questions

Why does it say 3 cans when I only need about 2.03 gallons?

Cans are only sold whole, so the planner always rounds up to the next full can of the size you entered. About 2.03 gallons (2.025) does not fit in 2 one-gallon cans, so you need 3. Mixing can sizes and other ways to reduce the leftover are covered in how pack rounding works. Do not count on returning an extra can: paint tinted to order is often handled differently from stock items, so ask the store first.

Should I subtract doors and windows?

Yes, for walls. Enter each door, window or other opening you will not paint with its width and height, and the planner takes it off the wall area. A small opening makes little difference, but large windows, patio doors or built-in units can change the result by a can. Do not subtract openings from the ceiling.

Where do I find the coverage number?

On the can or the product data sheet, usually as square feet per gallon or square meters per liter. That figure is for one coat. If the label gives a range, using the lower number is the cautious choice. More detail in paint coverage and coats.

Can I plan two colors or a primer in the same project?

Yes. Each color, finish and primer is its own material with its own coverage and can size. Rooms assigned to the same entry are added together before rounding; different colors or finishes are never added together, because you cannot pour one into the other.

Does the result include doors, frames, trim and stairs?

Only what you add. Walls and ceilings come from the room measurements; anything else you paint goes under Painted areas in step 1 as a rectangle (a door leaf: width × height) or a triangle. For stairs, the stairs helper adds a treads row and a risers row from the number of treads and risers, the stair width, the tread depth and the riser height; each row can take its own paint, and rows of the same paint are added up before rounding. Frames and trim are usually a different finish from a smaller can, so give them their own paint entry. Outdoor steps belong in the deck, fence and patio stain calculator.

Is a gallon and a quart cheaper than two or three gallons?

Only the prices can tell. In the feet example above, about 2.03 gallons is needed: 3 one-gallon cans cover it, and so would 2 gallons plus a quart (2.25 gallons). On the paint card, open Compare other can sizes of this paint, add the quart with its fill and price, and the planner shows the lowest total among the sizes and prices you entered, next to what one size alone would cost. The rounding behind it is explained in how pack rounding works.

My walls are textured, rough or newly plastered. Does that change the amount?

Usually it does: textured, rough and porous surfaces take more paint than a smooth, sealed wall, so the paint covers less than the label says. The planner adds no percentage of its own, so use the lower end of the label range or the label’s figure for rough surfaces. A mist coat or sealer coat of the same paint on new plaster counts as one more coat; a separate product goes on its own line, like a primer.

How many coats do I need for a big color change?

The planner does not decide; enter the coats from the label, and a primer the label asks for as its own material. Each extra coat adds the full wall area once more. In the metric example above, a third coat gives 32 × 3 ÷ 10 = 9.6 L, or 10.56 L with 10% allowance, which is 5 cans of 2.5 L (4.224 rounded up) instead of 3. More in paint coverage and coats.

How many epoxy kits, or cans of floor varnish or oil, do I need for a floor?

Ordinary wall paint is not planned on floors. For a garage floor, add a Floor coating kit in step 2 with the area one kit covers per coat: a 20 × 20 ft garage (400 ft²) with 250 ft² per kit, 2 coats and 10% extra needs 880 ÷ 250 = 3.52, so 4 kits, because a mixed kit cannot be split or kept. For a sanded wooden floor, add a Floor finish (clear varnish, polyurethane or floor oil) with the coverage and coats from its label. Follow the label for mixing, ventilation, drying times and sanding dust.

Will all my cans of one color match?

Cans tinted at different times can differ slightly. A common tip is to pour all the cans of one color into one large clean container and mix them before you start, so the whole job comes from one blend.

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