How to paint a room: Prep, coats & cleanup
Make a room-by-room paint list, prepare the surface and leave enough time between coats for the product you chose.
Paint quantity and surface preparation are different jobs. Enough cans will not fix a damp wall, loose coating or an unsuitable primer.
Separate the surfaces and colors
Measure walls, ceilings, doors and trim separately. Write the color and finish beside each surface. Combine quantities only where the same product can actually be shared. Keep one sample label or product reference with the plan so a second purchase does not silently become a different finish.
Inspect before buying repair supplies
Identify loose paint, cracks, stains and damp areas. Resolve a moisture source before covering its effects. If old coatings may contain lead, do not begin sanding or scraping without the appropriate lead-safe assessment and method. Sherwin-Williams’ surface-preparation guidance flags lead dust from disturbing old paint.
Protect, clean and repair
Sherwin-Williams’ How to Prep Walls for Painting describes protecting the room, cleaning, patching, caulking and priming as preparation tasks. Move or cover furniture, protect floors and remove or mask hardware. Let cleaned or repaired surfaces become ready for the selected coating before opening the finish paint.
Match primer and tools to the job
Use the coating maker’s substrate and primer instructions. Put brushes, roller covers, trays, masking materials, drop cloths and cleanup supplies on the shopping list, alongside paint and any primer. An existing color alone does not establish whether the surface needs sealing or a special primer.
Apply with the label beside you
Follow the product’s application method, ventilation requirements and recoat interval. Keep the wall and trim sequences in your room plan so freshly painted surfaces are not used as work supports. The calculator’s coats are your chosen input; check the actual coverage before committing the remaining paint to another room.
Check the finish and close the room
Inspect after the coating has dried as instructed. Mark touch-up locations and retain the product, color and finish names. Keep curing and cleaning instructions distinct from dry-to-touch time. A contractor quote should name preparation, protection, coats, repairs and cleanup, rather than just a room price.
See the measurement become an order
Example only: 12 × 10 ft room, 8 ft walls, 44 sq ft of openings and two chosen coats at the editable example coverage.
This example gives 2 1-gallon paint cans.
- Surface area: 308 sq ft
- ceil(308 × 2 × (1 + 0/100) ÷ 400) = 2