Paint Cost Calculator — Draw Your Room, Get Exact Gallons & Cost
Most paint calculators make you type wall measurements into boxes. This one lets you draw the room — pick a rectangle or L-shape (or draw your own walls), set the ceiling height, and place your real doors and windows. The planner computes the net wall area (openings subtracted), the ceiling, and the trim automatically, suggests coats and primer from your color change, adjusts coverage for wall texture, and turns it all into buyable cans, a supplies shopping list with typical big-box prices, and a DIY vs hire-it-out cost range. Free, no sign-up.
How to figure out paint the accurate way
Paint math is simple — area × coats ÷ coverage — but the area is where estimates go wrong. Walls get measured gross, doors and windows never get subtracted, and the trim and ceiling get forgotten until the third store run. Drawing the room fixes all of that at once: the planner reads the actual geometry — every wall at its drawn length times your ceiling height, minus every door (6'8") and window you placed — and keeps a separate tally for the ceiling, the baseboard, and the door and window casings.
The other place estimates fail is coats. A refresh in a similar shade often needs one coat; a normal color change needs two; going from dark to light (or covering red) usually means two coats plus a stain-blocking primer; and bare drywall drinks a PVA primer first. Pick your situation and the planner sets coats and primer for you — then adds a realistic 10% for cutting in and touch-ups, more if your walls are textured.
Standard room dimensions to design around
The numbers the planner uses — handy if you want to sanity-check by hand:
| Element | Standard size | Notes |
|---|---|---|
| Wall coverage | ~350 sq ft per gallon | Smooth, primed walls, per coat |
| Quart coverage | ~85 sq ft | For trim and small jobs |
| Door subtraction | ~17 sq ft (3'0" × 6'8") | Plus casing painted with trim |
| Window subtraction | ~12 sq ft typical | Sized from your drawn width |
| Texture penalty | +12–28% | Light texture → heavy knockdown |
| Waste / cut-in buffer | +10% | Touch-ups, roller & tray loss |
| Pro repaint rate | $1.50–3.50 / sq ft | Walls + ceilings, US typical |
Frequently asked questions
Is this paint calculator really free?
Yes — completely free with no account and no email. Drawing the room, the paint and supplies list, the cost estimate, and the CSV/PNG/print/DXF exports are all free.
How much paint do I need for a 12×12 room?
A 12×12 room with 8-foot ceilings has about 384 sq ft of wall before openings. With a door and a window subtracted and two coats, that's typically 2 gallons plus a quart of wall paint, one gallon of ceiling paint, and a quart or two of trim enamel. Draw your exact room above — the answer changes meaningfully with ceiling height and how many openings you have.
Does it subtract doors and windows?
Yes — that's the point of drawing the room. Each door you place removes about 17 sq ft and each window about 12 sq ft from the wall total, and door widths are also removed from the baseboard count. A 10% cut-in and touch-up buffer is added back so you don't run out mid-wall.
How many coats do I need — and do I need primer?
It depends on the color change, so the planner asks: a similar shade is usually one coat; a normal color change two; dark-to-light or covering strong reds is two coats over a stain-blocking primer; and new bare drywall needs a PVA primer first. You can always override the coat count manually.
What's the difference between builder, mid, and premium paint?
Mostly hide (how well it covers in fewer coats), scrub resistance, and finish quality. Builder-grade runs roughly $22–30 a gallon, mid-grade $35–48, and premium lines $55–80. The planner changes the price, not the gallons — though in practice premium paint's better hide is what makes one-coat refreshes realistic.
Should I DIY or hire a painter?
The planner shows both: your materials cost plus an estimated DIY time (at a realistic pace including prep and cutting in), next to a typical professional range of $1.50–3.50 per square foot of walls and ceiling. Painting is the most DIY-friendly trade there is — but stairwells, high ceilings, and major prep tilt the math toward a pro.
Keep planning
All the free CAD room planners
Every room runs on the same 2D CAD engine — draw to scale, drop in fixtures that snap into place, watch a live cost estimate build, and export a DXF for your contractor.