Multi-Room Paint Calculator & Shopping List

A paint calculator built for whole projects, not single walls

Most paint calculators answer one room at a time and forget it the moment you leave. That's not how painting actually goes — you're doing the hallway, two bedrooms and maybe the ceiling while the furniture is already shoved into the middle of the house. This calculator keeps a running list of every room, does the gallon math per room, and rolls it all into one shopping list you can print and take to the store. Your project stays saved in your browser, so when you finally get to the second bedroom next weekend, the plan is still here.

The method, step by step

1. Wall area: perimeter × ceiling height. A 12×12 room with 8-ft ceilings has 2 × (12 + 12) × 8 = 384 sq ft of gross wall.
2. Subtract openings: measure doors, windows and other surfaces that will not be painted. The tool does not assign them standard sizes.
3. Multiply by coats: two coats means painting the area twice. This is the step that turns a one-pass surface measurement into coated area.
4. Divide by coverage: replace the prefilled example with the selected product's label or technical-data spread rate, then compare sensitivity cases if it gives a range.
5. Trim and primer ride along separately, because you buy them separately. Enter measured trim face area and each selected product's coverage.

Separate products need separate cans

Consider one measured 10×10×8-ft room with 20 sq ft of unpainted openings. Two wall coats cover 600 coated sq ft. At an illustrative 350 sq ft/gal, that is 1.714 gallons: buy 1 gallon + 3 quarts. A 100-sq-ft ceiling with one coat at 400 sq ft/gal needs 1 quart of its own product. The two remaining quantities cannot be combined into a shared can if the colors or products differ.

Use the separate-ceiling option to apply two label rates and round two orders. If every surface uses the same product and color, turn it off to pool the coated area before rounding. The calculator keeps all rooms on one wall product; save or export separate projects for different wall colors.

What the shopping list rounds — and why

Exact math says things like "2.37 gallons", but stores sell gallons and quarts. The list rounds each total up to the nearest quart and converts four quarts into a gallon, so what you read is what you buy. If the wall total lands just over a whole gallon — say 2.05 — you'll see 2 gallons and 1 quart. Whether you actually buy the quart or stretch the gallons is your call; for the spare-paint side of that decision, our guide to leftover-paint math and records separates that choice from minimum package rounding.

Getting the inputs right

• Coverage is an explicit product input. Surface texture, porosity, condition and application affect spread. Use the selected product documentation and readhow coverage sensitivity changes the purchase.
• Set coats from the coating system and a test area. Color names alone cannot predict hiding; the dark-wall guide separates spread from hiding.
• Trim area: measure the paintable faces of baseboards, casings and other trim rather than assuming every linear foot has the same height or number of faces.
• Primer is a separate product. The checkbox adds one primer coat over the same area. When you actually need it (bare drywall, stains, drastic color changes) is covered inour primer decision guide.
• Cabinets need a component inventory. Doors have separate faces and frames do not scale reliably from room dimensions. Use the dedicatedkitchen cabinet paint calculator for that takeoff.

Frequently asked questions