{"success":true,"version":"v1","request":{"tool":"get_calculator_schema","calculator_id":"paint"},"result":{"entity_type":"calculator","id":"paint","calculator_id":"paint","canonical_url":"https://tttkmbb.com/construction/paint","name":"Paint Calculator","title":"Paint Calculator – Litres or Gallons of Wall Paint from Room Size, Doors, Windows and Coats","category":"construction","category_name":"Construction & Home","tool_name":"estimate_paint_needed","featured_mcp_tool":false,"description":"Estimates wall paint from the wall area (room length, width and height, or a given area), subtracting 1.9 m² per door and 1.4 m² per window, multiplying by the number of coats and dividing by the coverage rate; reports litres, US gallons and cans.","use_when":"You need to know how much paint to buy for the walls of a room or for a known wall area, in litres or gallons and cans.","do_not_use_when":"You need ceiling, floor or exterior siding paint with different coverage rates (enter the area and the product's coverage directly), or you need the wall area only (use rectangle).","inputs":[{"name":"unit_system","label":"Unit system","type":"enum","required":false,"default":"metric","values":[{"value":"metric","label":"Metric (m, cm, mm, m²)","aliases":["si","metres","meters"]},{"value":"imperial","label":"Imperial / US customary (ft, in, ft²)","aliases":["us","feet","inches"]}],"description":"Unit system of the length inputs (metric: m / cm / mm; imperial: ft / in). Outputs are reported in both systems.","example":"metric"},{"name":"room_length","label":"Room length","type":"number","unit":"m or ft","required":false,"max":1000,"exclusive_min":0,"description":"Room length (m or ft). Used with room_width and wall_height when wall_area is not given.","example":5},{"name":"room_width","label":"Room width","type":"number","unit":"m or ft","required":false,"max":1000,"exclusive_min":0,"description":"Room width (m or ft).","example":4},{"name":"wall_height","label":"Wall height","type":"number","unit":"m or ft","required":false,"max":100,"exclusive_min":0,"description":"Floor-to-ceiling height (m or ft).","example":2.4},{"name":"wall_area","label":"Total wall area","type":"number","unit":"m² or ft²","required":false,"exclusive_min":0,"description":"Gross wall area before openings (m² or ft²). When given, the room dimensions are ignored."},{"name":"doors","label":"Doors","type":"integer","required":false,"default":1,"min":0,"max":100,"description":"Number of doors; 1.9 m² (20.5 ft²) is subtracted per door.","example":1},{"name":"windows","label":"Windows","type":"integer","required":false,"default":1,"min":0,"max":100,"description":"Number of windows; 1.4 m² (15.1 ft²) is subtracted per window.","example":2},{"name":"coats","label":"Coats","type":"integer","required":false,"default":2,"min":1,"max":5,"description":"Number of coats. Two coats are standard for colour changes; primer is not included.","example":2},{"name":"coverage","label":"Coverage rate","type":"number","required":false,"exclusive_min":0,"description":"Coverage from the tin: m² per litre in metric (default 10) or ft² per US gallon in imperial (default 350). Typical emulsion covers 10–14 m²/L (350–400 ft²/gal).","example":10},{"name":"can_size","label":"Can size","type":"number","required":false,"exclusive_min":0,"description":"Litres per can (metric, default 5) or US gallons per can (imperial, default 1); used for the can count.","example":5}],"outputs":[{"name":"gross_wall_area_m2","label":"Gross wall area","type":"number","unit":"m²","decimals":2,"description":"2 × (length + width) × height, or wall_area."},{"name":"gross_wall_area_ft2","label":"Gross wall area","type":"number","unit":"ft²","decimals":2,"description":"Gross wall area in square feet."},{"name":"paintable_area_m2","label":"Paintable area","type":"number","unit":"m²","decimals":2,"description":"Gross area minus 1.9 m² per door and 1.4 m² per window."},{"name":"paintable_area_ft2","label":"Paintable area","type":"number","unit":"ft²","decimals":2,"description":"Paintable area in square feet."},{"name":"paint_liters","label":"Paint needed","type":"number","unit":"L","decimals":2,"description":"paintable_area × coats / coverage, in litres."},{"name":"paint_gallons","label":"Paint needed","type":"number","unit":"US gal","decimals":2,"description":"Same amount in US gallons (1 gal = 3.785 L)."},{"name":"cans_needed","label":"Cans to buy","type":"integer","decimals":4,"description":"ceil(paint needed / can_size)."},{"name":"can_size_used","label":"Can size used","type":"string","decimals":4,"description":"Can size assumed for the can count."}],"input_schema":{"type":"object","properties":{"unit_system":{"description":"Unit system of the length inputs (metric: m / cm / mm; imperial: ft / in). Outputs are reported in both systems.","type":"string","enum":["metric","imperial"],"default":"metric","examples":["metric"]},"room_length":{"description":"Room length (m or ft). Used with room_width and wall_height when wall_area is not given. Unit: m or ft.","type":"number","maximum":1000,"exclusiveMinimum":0,"examples":[5],"x-unit":"m or ft"},"room_width":{"description":"Room width (m or ft). Unit: m or ft.","type":"number","maximum":1000,"exclusiveMinimum":0,"examples":[4],"x-unit":"m or ft"},"wall_height":{"description":"Floor-to-ceiling height (m or ft). Unit: m or ft.","type":"number","maximum":100,"exclusiveMinimum":0,"examples":[2.4],"x-unit":"m or ft"},"wall_area":{"description":"Gross wall area before openings (m² or ft²). When given, the room dimensions are ignored. Unit: m² or ft².","type":"number","exclusiveMinimum":0,"x-unit":"m² or ft²"},"doors":{"description":"Number of doors; 1.9 m² (20.5 ft²) is subtracted per door.","type":"integer","minimum":0,"maximum":100,"default":1,"examples":[1]},"windows":{"description":"Number of windows; 1.4 m² (15.1 ft²) is subtracted per window.","type":"integer","minimum":0,"maximum":100,"default":1,"examples":[2]},"coats":{"description":"Number of coats. Two coats are standard for colour changes; primer is not included.","type":"integer","minimum":1,"maximum":5,"default":2,"examples":[2]},"coverage":{"description":"Coverage from the tin: m² per litre in metric (default 10) or ft² per US gallon in imperial (default 350). Typical emulsion covers 10–14 m²/L (350–400 ft²/gal).","type":"number","exclusiveMinimum":0,"examples":[10]},"can_size":{"description":"Litres per can (metric, default 5) or US gallons per can (imperial, default 1); used for the can count.","type":"number","exclusiveMinimum":0,"examples":[5]}},"additionalProperties":false},"output_schema":{"type":"object","properties":{"gross_wall_area_m2":{"description":"2 × (length + width) × height, or wall_area. Unit: m².","type":"number","x-unit":"m²"},"gross_wall_area_ft2":{"description":"Gross wall area in square feet. Unit: ft².","type":"number","x-unit":"ft²"},"paintable_area_m2":{"description":"Gross area minus 1.9 m² per door and 1.4 m² per window. Unit: m².","type":"number","x-unit":"m²"},"paintable_area_ft2":{"description":"Paintable area in square feet. Unit: ft².","type":"number","x-unit":"ft²"},"paint_liters":{"description":"paintable_area × coats / coverage, in litres. Unit: L.","type":"number","x-unit":"L"},"paint_gallons":{"description":"Same amount in US gallons (1 gal = 3.785 L). Unit: US gal.","type":"number","x-unit":"US gal"},"cans_needed":{"description":"ceil(paint needed / can_size).","type":"integer"},"can_size_used":{"description":"Can size assumed for the can count.","type":"string"}}},"formula":"gross = 2 × (room_length + room_width) × wall_height (or wall_area); paintable = gross − 1.9 m² × doors − 1.4 m² × windows; litres = paintable_m² × coats / coverage_m²_per_L; gallons = litres / 3.785; cans = ceil(litres / can_size). Imperial coverage: ft²/gal × 0.09290304 / 3.785411784 = m²/L.","method":"The door (1.9 m² ≈ 0.9 × 2.1 m) and window (1.4 m²) deductions are conventional averages; real coverage depends on surface texture, porosity, colour change and application method, so read the coverage figure from the product label.","sources":[{"name":"Sherwin-Williams – Paint calculator FAQ (a gallon covers about 350–400 sq ft)","url":"https://www.sherwin-williams.com/en-us/color/color-tools/paint-calculator","type":"reference","retrieved_at":"2026-09-23"},{"name":"Dulux – Paint calculator (coverage varies by surface and product)","url":"https://www.dulux.co.uk/en/paint-calculator","type":"reference","retrieved_at":"2026-09-23"}],"freshness":{"type":"static","max_age_seconds":null,"note":"Deterministic formula with fixed constants; results never go stale. Inputs supplied by the caller determine the output."},"examples":[{"name":"5 m × 4 m × 2.4 m, 1 door, 2 windows, 2 coats, 10 m²/L, 5 L cans","inputs":{"unit_system":"metric","room_length":5,"room_width":4,"wall_height":2.4,"doors":1,"windows":2,"coats":2,"coverage":10,"can_size":5},"expected":{"gross_wall_area_m2":43.2,"gross_wall_area_ft2":465,"paintable_area_m2":38.5,"paintable_area_ft2":414.41,"paint_liters":7.7,"paint_gallons":2.03,"cans_needed":2,"can_size_used":"5 L"},"url":"https://tttkmbb.com/api/v1/calculate/paint?unit_system=metric&room_length=5&room_width=4&wall_height=2.4&doors=1&windows=2&coats=2&coverage=10&can_size=5"},{"name":"15 ft × 12 ft × 8 ft, 2 doors, 2 windows, 2 coats, 350 ft²/gal, 1 gal cans","inputs":{"unit_system":"imperial","room_length":15,"room_width":12,"wall_height":8,"doors":2,"windows":2,"coats":2},"expected":{"gross_wall_area_ft2":432,"gross_wall_area_m2":40.13,"paintable_area_ft2":360.96,"paint_gallons":2.06,"paint_liters":7.81,"cans_needed":3,"can_size_used":"1 gal"},"url":"https://tttkmbb.com/api/v1/calculate/paint?unit_system=imperial&room_length=15&room_width=12&wall_height=8&doors=2&windows=2&coats=2"}],"faq":[{"q":"Does this include primer or the ceiling?","a":"No. Primer covers only 200–300 ft²/gal (5–7 m²/L) and is estimated separately; for the ceiling enter its area as wall_area with doors = 0 and windows = 0."},{"q":"Why litres and gallons at the same time?","a":"Paint is sold in litres in most countries and in US gallons/quarts in the USA; both are reported from the same paintable area so either label can be used."},{"q":"What if coverage is given per coat on the tin?","a":"Coverage rates on labels are always per coat; this calculator multiplies by the number of coats, so enter the label value unchanged."}],"tags":["paint calculator","how much paint","litres of paint","gallons of paint","wall area","coats"],"related":[{"calculator_id":"wallpaper","reason":"Rolls of wallpaper for the same walls."},{"calculator_id":"drywall","reason":"Sheets of plasterboard for the same walls."},{"calculator_id":"flooring","reason":"Floor material for the same room."}],"links":{"html":"https://tttkmbb.com/construction/paint","markdown":"https://tttkmbb.com/construction/paint.md","json":"https://tttkmbb.com/construction/paint.json","api":"https://tttkmbb.com/api/v1/calculate/paint","schema":"https://tttkmbb.com/api/v1/calculators/paint","openapi":"https://tttkmbb.com/openapi.json","mcp":"https://tttkmbb.com/mcp"},"version":"v1","updated_at":"2026-09-23"},"timestamp":"2026-09-23T23:23:14Z"}