The job
Modelled, not recorded. Every figure on this page is re-run through the calculator it names whenever the site is built; the estimate is worked, but no job was carried out, so the last section gives the mechanism of each likely error rather than a measured overrun.
Repainting a bedroom sounds like one purchase and is really five: a wall finish, a primer, a ceiling white, a trim enamel, and the drop cloths and tape that keep all four off the floor. They are sold as separate products, rated at separate spread rates and measured from separate parts of the room — the walls from the perimeter, the ceiling from the floor, the trim from lengths and girths — so each gets its own figure here rather than a slice of one gallon count.
The job: a 12 × 14 ft (3.7 × 4.3 m) bedroom with an 8 ft (2.4 m) ceiling, one flush door and one vinyl window, taken as a plain rectangle with no closet and the furniture moved out. The walls are a deep charcoal going to an off-white. The ceiling is a sound flat white staying white, planned at two coats, which is the ceiling page's usual finish, though a single coat can do over a sound ceiling in the same white. The baseboard, casings and door are a sound white semi-gloss repainted in the same white, also at two coats.
THE FIGURE THAT DECIDES THE WALLS IS THE COAT COUNT, and the tape measure cannot supply it. Wall area is geometry and is settled in minutes; what charcoal does to an off-white film is not, and between the primed route and the unprimed one it doubles the finish paint. So the paint calculator is run for a single coat — a unit of paint rather than an order — and the number of coats is decided one step later, where both routes are laid out side by side.
THE TAKEOFF ORDER IS NOT THE PAINTING ORDER. On the day the ceiling goes on first, then the walls, then the trim. On paper the walls come first because they hold the only open decision: whether to prime, which sets the primer line and the number of finish cans, and the finish cans are what the last step blends. The ceiling and the trim are like-for-like and cannot change anything upstream of them.
NOTHING HERE WAS PAINTED. Each quantity comes out of the calculator named at its step, fed the inputs printed with it, so any line can be reopened and will give the same answer. Two purchases a repaint almost always makes carry no quantity — spackle for dents and nail holes, and caulk for the gaps where trim meets wall — because no page on this site sizes either as spot work in a room like this; they are listed as gaps instead. The closing section names the places this list is most likely to miss and which way each one pulls, argued from how the error arises, since there is no finished room to check it against.
What was measured, and how
Room size at floor level, in both directions
12 × 14 ft (3.66 × 4.27 m): 168 sq ft (15.6 m²) of floor and 52 ft (15.8 m) of perimeter
Taped wall to wall along the floor both ways, then again at about shoulder height, and the larger figure kept. Measuring from the face of the baseboard rather than the drywall shortens every run slightly, and a closet or a return left off the sketch is wall that still gets painted.
Ceiling height, read at more than one corner
8 ft (2.44 m), giving 416 sq ft (38.6 m²) of gross wall
Floor to ceiling at two or three corners rather than once mid-wall, and on the subfloor or hard floor rather than over carpet pile. A single low reading under-reports all four walls at once, because the one height is applied to the whole perimeter.
Openings, measured across the outside of the casing
A 30 × 80 in (0.76 × 2.03 m) flush door and a 3 × 4 ft (0.91 × 1.22 m) window, each cased in 2½ in (64 mm) trim: about 35 × 82½ in (0.89 × 2.10 m) over the door casing and 41 × 53 in (1.04 × 1.35 m) over the window's, or 20.1 and 15.1 sq ft (1.86 and 1.40 m²)
The wall paint stops at the casing's outer edge and the trim paint starts there, so the deduction is the opening measured over its casing, not the leaf or the glass. Measured that way, both openings sit within about a square foot of the calculator's standard allowances — about 21 sq ft (1.95 m²) a door and 15 sq ft (1.4 m²) a window — so those stay at default. The window is vinyl, so its frame and sash take no paint; only the wood casing round it does.
Trim runs and their painted girths
49 ft (14.9 m) of 3½ in (89 mm) baseboard at a 4 in (102 mm) girth; 32 ft (9.75 m) of casing, about 16 ft (4.9 m) round each opening, at a 6 in (152 mm) girth
Baseboard runs the perimeter less the width of the door casing. Casing is run once round the door on the bedroom side only — the leaf is painted on both faces, because a door finished on one side shows the change along its edges, but the hall-side casing is the hallway's trim — and once round the window, which is cased on all four sides with no stool or apron. Each girth comes off a strip of paper pressed into the profile, from the casing's outer edge into the jamb as far as the stop or the window frame; reading it from the board's nominal width misses the moulded edge and the jamb.
What is on each surface now, and the spread rate on each can
Wall finish and ceiling flat 350 sq ft/gal (8.6 m²/L); tinted primer 300 sq ft/gal (7.4 m²/L); trim enamel 400 sq ft/gal (9.8 m²/L)
Walls, ceiling and trim are judged separately, because only the walls change colour. Every spread rate is read off the product actually being bought, and the primer's is the figure printed for a previously painted wall — using its bare-drywall figure here would overstate the primer by half.
The takeoff, in order
Each step needs something from the one before it, which is why the order is part of the answer.
Sheet the floor and count the tape
- Needs
- The 168 sq ft (15.6 m²) floor and 52 ft (15.8 m) perimeter from the measurements, each 9 × 12 ft (2.7 × 3.7 m) cloth taken at 100 sq ft (9.3 m²) once overlapped, two taped lines at the baseboard top and the ceiling, and 16 ft (4.9 m) of casing round each of the two openings — tape follows edges, so frames count as lengths.
- Produces
- Two drop cloths and one 60 yd (55 m) roll of painter's tape. It comes first because the cloths go down before any patching or sanding, and the floor area it uses is the figure the ceiling step takes later.
Result3 items: 2 drop cloths and 1 roll of tape for 136 ft (41.5 m) of edge
Masking and Protection Materials CalculatorWork out one coat of wall paint
- Needs
- The 12 × 14 ft (3.7 × 4.3 m) plan and 8 ft (2.4 m) height from the measurements, and the same door and window that step one taped round, deducted at the calculator's standard allowances. Run at one coat on purpose: how many coats is the next step's question.
- Produces
- 380 sq ft (35.3 m²) of net wall and the paint for a single coat over it at 350 sq ft/gal (8.6 m²/L). The per-coat volume is what step three multiplies; the net area is what step four primes.
Result1.09 gal (4.1 L) for one coat over 380 sq ft (35.3 m²) of net wall
Paint CalculatorDecide the coat count over charcoal
- Needs
- The one-coat volume from step two, and a judgement of how far the charcoal sits below the off-white — much darker, which on its own means four coats of finish with nothing underneath.
- Produces
- A coat of primer tinted toward the off-white, then two finish coats. The finish itself is 2.17 gal (8.2 L); the unprimed route would be four finish coats and 4.34 gal (16.4 L). The headline counts the primer coat at the finish paint's rate, which step four corrects.
Result3.26 gal (12.3 L): one tinted primer coat and two finish coats, 2.17 gal (8.2 L) of it finish
Paint Coverage Over Dark Colours CalculatorQuantify the primer at its own spread rate
- Needs
- The 380 sq ft (35.3 m²) of net wall from step two and the decision at step three to prime it, at the rate the primer can gives for a previously painted surface — 300 sq ft/gal (7.4 m²/L), below the finish paint's.
- Produces
- 1.5 gal (5.7 L), rounded up from 1.27 gal (4.8 L) to the half gallon and bought as a gallon and two quarts. Step three had the primer coat at 1.09 gal (4.1 L) because it assumed the finish paint's spread; this is the figure to order.
Result1.5 gal (5.7 L) of primer tinted toward the off-white
Paint Primer CalculatorQuantify the ceiling white
- Needs
- The 168 sq ft (15.6 m²) floor area that sized the drop cloths at step one — a flat ceiling covers exactly the floor — with two coats of flat white at 350 sq ft/gal (8.6 m²/L) and nothing to deduct.
- Produces
- The bare film for two coats, just under one gallon (3.8 L), which leaves a single gallon can with no margin for what overhead rolling loses. A different product from the walls, so it is never blended with them.
Result0.96 gal (3.6 L) of flat white for two coats
Ceiling Paint CalculatorQuantify the trim enamel for baseboard, casing and door
- Needs
- The door step two took off the wall, now counted as paintable surface on both faces; step one's 52 ft (15.8 m) perimeter less the 3 ft (0.9 m) the door casing spans, as baseboard; and the 32 ft (9.75 m) of casing step one taped round, each at its measured girth.
- Produces
- 65.7 sq ft (6.1 m²) of woodwork, two coats at 400 sq ft/gal (9.8 m²/L) — more than a quart (0.95 L) holds, so two quarts (1.9 L). The door's two faces, 33.3 sq ft (3.1 m²), are about half that area, and more than the 21 sq ft (1.95 m²) step two deducted for the whole opening.
Result0.33 gal (1.24 L) of trim enamel for two coats over 65.7 sq ft (6.1 m²)
Woodwork Paint CalculatorPlan the blend of the wall finish
- Needs
- The 2.17 gal (8.2 L) of finish from step three, rounded up to three one-gallon (3.8 L) cans because it carries nothing for the tray or roller cover; two batch codes assumed across the three cans, since nothing has been bought to read them from; and a 5 gal (18.9 L) bucket to blend in.
- Produces
- One container: three gallons (11.4 L) fit in the bucket with room left to stir, so all four walls come out of one blend and none shows a step where a can ended. If all three cans carry one code, the page calls the blend optional rather than wrong, since it still evens out how well each can was stirred. It comes last because it needs the can count, which needed the coat count.
Result1 container: 3 gal (11.4 L) blended in one 5 gal (18.9 L) bucket
Paint Boxing Calculator — Blending Tins Before You Start
The figures
| Step | Calculator | Figure |
|---|---|---|
| Sheet the floor and count the tape | Masking and Protection Materials Calculator | 3 items: 2 drop cloths and 1 roll of tape for 136 ft (41.5 m) of edge |
| Work out one coat of wall paint | Paint Calculator | 1.09 gal (4.1 L) for one coat over 380 sq ft (35.3 m²) of net wall |
| Decide the coat count over charcoal | Paint Coverage Over Dark Colours Calculator | 3.26 gal (12.3 L): one tinted primer coat and two finish coats, 2.17 gal (8.2 L) of it finish |
| Quantify the primer at its own spread rate | Paint Primer Calculator | 1.5 gal (5.7 L) of primer tinted toward the off-white |
| Quantify the ceiling white | Ceiling Paint Calculator | 0.96 gal (3.6 L) of flat white for two coats |
| Quantify the trim enamel for baseboard, casing and door | Woodwork Paint Calculator | 0.33 gal (1.24 L) of trim enamel for two coats over 65.7 sq ft (6.1 m²) |
| Plan the blend of the wall finish | Paint Boxing Calculator — Blending Tins Before You Start | 1 container: 3 gal (11.4 L) blended in one 5 gal (18.9 L) bucket |
The waste factors, and why these ends of the ranges
| Material | Applied | Why |
|---|---|---|
| Off-white wall finish | Rounded up to whole gallon cans, with no percentage added on top | The 2.17 gal (8.2 L) is film on the wall and nothing else — the paint calculator allows nothing for the tray, the roller cover or touch-ups. Two gallons and a quart (8.5 L) would clear it by about 0.08 gal (0.3 L), well under a pint (0.47 L), a margin a loaded tray and roller cover swallow between them, so the order goes to three gallons (11.4 L), and what stays in the bucket afterwards is touch-up stock from the same blend. |
| Tinted primer | The half-gallon rounding the calculator applies, and nothing more | Rounding 1.27 gal (4.8 L) up to 1.5 gal (5.7 L) already puts about 18% over the film, and a primer is a single coat that only has to hide and seal, with no finish sheen to lay off evenly. Tinted product is also usually not returnable, so a deliberate surplus is money that sits in the garage. |
| Ceiling white | The overhead allowance the ceiling page itself suggests, which tips it past one can | At 0.96 gal (3.6 L) one gallon (3.8 L) has nothing to spare, and rolling overhead loses more to spatter and to the roller cover than wall work does. The ceiling calculator's own guidance puts a common allowance on a smooth ceiling at about 10%, which lands just over the gallon — so a gallon and a quart (4.7 L). |
| Trim enamel | Rounded up to whole quarts — two of them | 0.33 gal (1.24 L) is more than one quart (0.95 L) and well inside two. Brushing into casing profiles and cutting in against a freshly painted wall uses paint no area captures, and the second quart carries that with room to spare. |
| Drop cloths and tape | Whole cloths and whole rolls, with the cloths treated as reusable | Two cloths cover the 168 sq ft (15.6 m²) floor once overlapped, but only an empty floor: a bed or dresser left in the room needs its own cover, which no floor area measures. The tape count assumes each line is taped once, just before the paint that meets it: the ceiling line before the walls are cut in, then the baseboard top and the casing edges on the dry wall paint before the trim coats. The single 180 ft (55 m) roll leaves 44 ft (13.4 m) spare against 136 ft (41.5 m) of edge — less than one lap of the baseboard, so any line taped a second time means a second roll. |
Where this estimate is most likely to be wrong
Coats of wall finish
usually underPrimer plus two finish coats is a planning figure and two is a floor rather than a middle — nothing brings an even film below it. The only way the count moves is up: a charcoal with a blue or green cast, a primer tinted too light, or a finish with poor hiding can leave a shadow after the second coat, and a third coat is another 1.09 gal (4.1 L).
Narrow it by: Putting primer and two finish coats on a test patch on the darkest wall before ordering the full quantity, and judging it dry in daylight.
Net wall area
either wayThe paint calculator reads the room as a closed rectangle at one height. A closet, a window set in a deep return, or a ceiling a little over 8 ft (2.4 m) all add wall the plan does not show. The one surface counted twice pulls the other way: the baseboard's face along 49 ft (14.9 m), about 14 sq ft (1.3 m²) at 3½ in (89 mm) tall, sits inside the 380 sq ft (35.3 m²) and is painted again in enamel at step six. That over-count is small, does not take the finish below two gallons (7.6 L), and a single closet would outweigh it. The door and window allowances sit within a square foot of this room's casings, so the deductions have little room to move.
Narrow it by: Walking the room with the tape and listing every surface the roller will touch that the plan leaves out, closet walls first.
Ceiling white
either wayAt the two coats planned, the losses all run one way: a roller working above head height sheds droplets onto the cloths, a long-nap cover soaks up more before any reaches the surface, and any patched spots absorb more of the first coat than the second. Against that, the ceiling is sound white staying white, and a single coat that hides evenly would make this line about twice what goes on. The quantity sits so close to one gallon (3.8 L) that either outcome changes the order by a can.
Narrow it by: Rolling the first coat from the gallon and judging it dry in daylight before buying anything more: a coat that hides evenly ends the ceiling there, and only a second coat needs the quart.
Woodwork area
usually underThe door is counted as two flat faces of a flush leaf, so its four edges are outside the figure, and a panelled leaf would carry noticeably more surface than its outline. The casing girth is read on a paper strip, and a strip that bridges a bead or a quirk instead of following it into the profile reads short. Both simplifications leave surface out rather than adding it.
Narrow it by: Adding the door's edges to the area and reading each girth twice with the strip pushed into every recess before ordering — both are small against the second quart's margin.
Primer spread rate
either wayThe primer is taken at the can's rate for a previously painted wall. Sanded spackle, torn drywall paper and bare patches soak up far more than a sealed latex film, while a sound, smooth wall can beat the printed figure. Which way it lands depends on how much patching the preparation turns up, and that is not known until the patching is finished.
Narrow it by: Patching and sanding before buying the primer, then spot-priming the patches so the full coat goes onto a surface that absorbs evenly.
Spackle and caulk, which are not on this list
usually underNo calculator on this site sizes spot patching on a painted wall. The room-repaint takeoff linked here does carry a compound row, but at the joint compound page's full skim rate with a note to scale it down for spot filling, so it is an upper bound rather than a figure for this room; and the caulk page is built around exterior door and window openings. Both are therefore missing from these quantities rather than estimated, and a repaint almost always buys both.
Narrow it by: Walking the walls with a light held flat against them, marking every hole and open joint, and buying spackle and caulk to that survey.
Tools this job needs
Frequently asked questions
- How much paint do I need for a 12 × 14 bedroom?
- With an 8 ft (2.4 m) ceiling, one door and one window, the walls are about 380 sq ft (35.3 m²) net; one coat at 350 sq ft/gal (8.6 m²/L) is 1.09 gal (4.1 L). Over charcoal that means 1.5 gal (5.7 L) of tinted primer, then two finish coats of 2.17 gal (8.2 L), bought as three gallons (11.4 L). The ceiling takes 0.96 gal (3.6 L) for two coats, ordered as a gallon and a quart (4.7 L), and the trim 0.33 gal (1.24 L).
- Do I need primer to paint off-white over a dark colour?
- Not strictly, but over a deep charcoal the unprimed route is modelled at four coats of finish — 4.34 gal (16.4 L) on this room's walls. A primer tinted toward the off-white brings it down to primer plus two finish coats: 2.17 gal (8.2 L) of finish and 1.5 gal (5.7 L) of primer at the primer's own spread rate. Two finish coats remain the floor whatever goes underneath, and a test patch settles the rest.
- How much trim paint do I need for a bedroom?
- Little by volume, more than most people allow by area. In this room 49 ft (14.9 m) of baseboard, 32 ft (9.75 m) of casing and one flush door painted on both faces come to 65.7 sq ft (6.1 m²). Two coats of trim enamel at 400 sq ft/gal (9.8 m²/L) is 0.33 gal (1.24 L), more than one quart (0.95 L) holds, so two quarts (1.9 L). The door's two faces are about half the area.