Understanding your result
The headline gives the paint for each colour, lower first, and the sub-line turns both into cans. The three figures are the paintable area of each colour after openings, and the rolls of tape for the colour line.
The table shows the perimeter, the two areas with the split height in their labels, the paint for each colour with its coats and allowance, and the length of colour line. The arithmetic below it shows how much of each door and window came out of each colour, which is the part a rough split by thirds gets wrong.
Two colours means two sets of rounding. A room that would need a gallon and a half in one colour may need three quarts of one and a gallon and two quarts of the other, so a two-tone room usually costs a little more than the same room in one colour. The wall paint calculator gives the one-colour figure to compare, the accent wall calculator handles a single wall in a strong colour, and the coats calculator tells you when the darker colour needs a third coat.
How we calculate this
Each door is taken as 36 × 80 in and each window as 36 × 60 in with its sill 36 in from the floor, the standard sizes listed in the standard sizes reference. The calculator measures how much of each opening falls below and above the split. With a 32 in split, a door takes 8 sq ft from the lower colour and 12 from the upper, and the window takes nothing from the lower colour because its sill is above the line.
The coverage is 350 sq ft per gallon per coat, the low end of interior wall paint data sheets, and the 5% allowance covers the roller and a touch-up jar. The coverage rates table lists the figures for other products. The colour line skips doorways because there is no wall to paint there, and a 60 yd roll of painter’s tape is 180 ft.
The assumptions behind the numbers
| Assumption | Default | Where it comes from |
|---|---|---|
| Coverage per coat | 350 sq ft per gallon | Interior wall paint data sheets (Sherwin-Williams, Benjamin Moore, Behr): 350–400 sq ft per gallon |
| Coats | 2 each colour | Manufacturers’ recommendation for a colour change |
| Allowance | 5% | Roller loss and a touch-up jar |
| Door | 36 × 80 in | The standard US interior door |
| Window | 36 × 60 in, sill at 36 in | A common double-hung window size and sill height |
| Painter’s tape | 60 yd (180 ft) per roll | The standard roll length of the major brands |
Assumptions last reviewed October 8, 2026.
The calculator assumes every wall is split at the same height and every opening is the standard size. A room with a large picture window or a patio door is closer if you count the big opening as two windows or two doors. Stairwells, where the split line runs diagonally, are a job for the stairwell calculator with the area divided by eye. The two-tone walls guide covers proportions, colour pairs and getting a level line round a room.
Two worked examples
A bedroom with a chair-rail split
A 12 × 12 ft room with 8 ft walls, one door and one window, split at 32 in, two coats of each colour.
- Perimeter: 2 × (12 + 12) = 48 ft
- Lower: 48 ft × 32 in = 128 sq ft, less 8 sq ft of door = 120 sq ft
- Upper: 48 ft × 64 in = 256 sq ft, less 12 sq ft of door and 15 sq ft of window = 229 sq ft
- Lower paint: 120 ÷ 350 × 2 × 1.05 = 2.88 quarts, buy 3 quarts
- Upper paint: 229 ÷ 350 × 2 × 1.05 = 1.37 gallons, buy 1 gallon + 2 quarts
- Colour line: 48 − 3 = 45 ft, 1 roll of tape
The window sits entirely above the line, so none of it comes off the lower colour. Splitting the openings by thirds would have put 5 sq ft of window into the lower colour and short-changed the upper.
A hallway with a taller wainscot
A 20 ft run of hallway wall, 9 ft high, two doors and no windows, split at 36 in.
- Lower: 20 ft × 36 in = 60 sq ft, less 2 doors × 9 sq ft = 42 sq ft
- Upper: 20 ft × 72 in = 120 sq ft, less 2 doors × 11 sq ft = 98 sq ft
- Lower paint: 42 ÷ 350 × 2 × 1.05 = 1.01 quarts, buy 2 quarts
- Upper paint: 98 ÷ 350 × 2 × 1.05 = 2.35 quarts, buy 3 quarts
- Colour line: 20 − 2 × 3 = 14 ft, 1 roll of tape
The lower colour is a hair over a quart, and the 5% allowance is what tips it. A careful painter with a durable scrubbable lower colour may manage on one quart; buying two keeps a touch-up supply for the part of a hallway that gets scuffed most.
Where to find your inputs
Room or wall length. Measure along the baseboard. For a single wall or a hallway, choose “a run of wall” and enter the total length of the walls that will be two-tone.
Wall height. Floor to ceiling in the corner.
Split height. The top of the chair rail, the top of the wainscot panelling, or the line you have marked. About a third of the wall height is the traditional starting point.
Doors and windows. Count them. The calculator splits each one at the line, so do not subtract them yourself.
Coverage. From the can. Deep-base colours often quote the low end of the range.
Common mistakes
- Splitting the paint by thirds. Doors and windows do not split evenly, and the error lands on the colour you have least of.
- Painting the dark colour first. Paint the light colour first and seal the tape with it, so any bleed is invisible.
- Measuring the split from the ceiling. Measure up from the floor at several points; floors are usually more level than ceilings, and a level line beats a parallel one.
- Splitting at half height. It divides the room in two; a third or two thirds looks intentional.
- Forgetting the moulding. A chair rail needs trim enamel, which is a separate quart.
- Mixing leftovers. Keep both colours sealed separately; the lower colour is the one you will touch up.
Questions people ask
- How much paint for a two-tone room?
- A 12 × 12 ft room with 8 ft walls split at 32 in, one door and one window, has 120 sq ft below the line and 229 above. At two coats and 350 sq ft per gallon that is 2.88 quarts of the lower colour, so three quarts, and 1.37 gallons of the upper, so a gallon and two quarts.
- What height should the split be?
- The traditional chair-rail height is about a third of the wall, 32 to 36 in on an 8 ft wall. Two thirds works for a tall wainscot or board and batten. Halfway cuts the room in two and is the one height designers avoid, which is why the calculator adds a note when the split is near the middle.
- Which colour goes on first?
- The lighter one, over the whole area it covers plus a little past the line. When it is dry, tape the line, seal the tape edge with a thin coat of the same light colour, and then paint the darker colour. Any bleed under the tape is in the colour that is already there, so the line comes out sharp.
- How much tape do I need?
- The colour line runs round the room once, less the doorways it does not cross. A 12 × 12 ft room with one door has a 45 ft line, well inside one 60 yd roll. The calculator gives the length and the rolls.
- Does a chair rail change the paint?
- Very little; the moulding covers a strip a couple of inches high where the colours meet. It changes the work, because there is no taped line to get straight, and it needs its own trim paint, which the trim calculator covers.
- Should the darker colour go on the bottom?
- Usually. A darker lower wall hides scuffs from chairs, shoes and vacuum cleaners and grounds the room visually, while the lighter upper wall keeps the room bright. Reversing it works in tall rooms but makes the scuffs show.