{"success":true,"version":"v1","request":{"tool":"get_calculator_schema","calculator_id":"room-lighting"},"result":{"entity_type":"calculator","id":"room-lighting","calculator_id":"room-lighting","canonical_url":"https://tttkmbb.com/energy/room-lighting","name":"Room Lighting Calculator","title":"Room Lighting Calculator – Lumens, Number of Bulbs and LED Wattage from Room Area and Target Lux","category":"energy","category_name":"Home Energy & Electrical","tool_name":"calculate_room_lighting","featured_mcp_tool":false,"description":"Computes the lumens a room needs from its floor area and a target illuminance (by room type or a custom lux value) divided by a light-loss factor, then the number of bulbs and the wattage at a given luminous efficacy.","use_when":"You are choosing how many LED bulbs or fixtures a room needs, or converting a lux requirement into lumens and watts.","do_not_use_when":"You need a photometric design with fixture spacing, beam angles or uniformity (use lighting-design software), or only the running cost of the lights (use electricity-cost).","inputs":[{"name":"floor_area_m2","label":"Floor area","type":"number","unit":"m²","required":true,"max":100000,"exclusive_min":0,"description":"Floor area of the room in square metres.","example":20},{"name":"room_type","label":"Room type","type":"enum","required":true,"values":[{"value":"living_room","label":"Living room (150 lux)","aliases":["lounge"]},{"value":"bedroom","label":"Bedroom (100 lux)"},{"value":"kitchen","label":"Kitchen (300 lux)"},{"value":"bathroom","label":"Bathroom (200 lux)"},{"value":"home_office","label":"Home office / study (500 lux)","aliases":["office","study"]},{"value":"workshop","label":"Workshop / garage bench (750 lux)","aliases":["garage"]},{"value":"hallway","label":"Hallway / stairs (100 lux)","aliases":["corridor"]},{"value":"dining","label":"Dining room (200 lux)","aliases":["dining_room"]},{"value":"custom","label":"Custom (give target_lux)"}],"description":"Room type selecting a typical maintained illuminance (EN 12464-1 / IES ranges); use custom with target_lux for other values.","example":"home_office"},{"name":"target_lux","label":"Target illuminance","type":"number","unit":"lux","required":false,"max":100000,"exclusive_min":0,"description":"Optional illuminance in lux that overrides the room-type value; required when room_type is custom.","example":500},{"name":"lumens_per_bulb","label":"Lumens per bulb","type":"number","unit":"lm","required":false,"default":800,"max":100000,"exclusive_min":0,"description":"Light output of one bulb or fixture (800 lm ≈ a 60 W incandescent equivalent, 1,100 lm ≈ 75 W, 1,600 lm ≈ 100 W).","example":800},{"name":"light_loss_factor","label":"Light loss factor","type":"number","required":false,"default":0.8,"min":0.3,"max":1,"description":"Maintenance / utilisation factor for dirt, lamp ageing and light absorbed by walls (0.8 typical for light rooms, 0.6–0.7 for dark ones).","example":0.8},{"name":"luminous_efficacy_lm_per_w","label":"Luminous efficacy","type":"number","unit":"lm/W","required":false,"default":100,"min":5,"max":300,"description":"Lumens per watt of the light source: LED 80–150, CFL 50–70, halogen 15–25, incandescent 10–17.","example":100}],"outputs":[{"name":"target_lux_used","label":"Target illuminance","type":"number","unit":"lux","decimals":0,"description":"Illuminance used for the calculation."},{"name":"required_lumens","label":"Required lumens","type":"number","unit":"lm","decimals":0,"description":"target_lux × floor_area_m2 / light_loss_factor."},{"name":"bulbs_needed","label":"Bulbs needed","type":"integer","decimals":0,"description":"required_lumens / lumens_per_bulb, rounded up."},{"name":"installed_lumens","label":"Installed lumens","type":"number","unit":"lm","decimals":0,"description":"bulbs_needed × lumens_per_bulb."},{"name":"total_wattage_w","label":"Total wattage","type":"number","unit":"W","decimals":1,"description":"required_lumens / luminous_efficacy_lm_per_w."},{"name":"watts_per_m2","label":"Lighting power density","type":"number","unit":"W/m²","decimals":2,"description":"total_wattage_w / floor_area_m2."}],"input_schema":{"type":"object","properties":{"floor_area_m2":{"description":"Floor area of the room in square metres. Unit: m².","type":"number","maximum":100000,"exclusiveMinimum":0,"examples":[20],"x-unit":"m²"},"room_type":{"description":"Room type selecting a typical maintained illuminance (EN 12464-1 / IES ranges); use custom with target_lux for other values.","type":"string","enum":["living_room","bedroom","kitchen","bathroom","home_office","workshop","hallway","dining","custom"],"examples":["home_office"]},"target_lux":{"description":"Optional illuminance in lux that overrides the room-type value; required when room_type is custom. Unit: lux.","type":"number","maximum":100000,"exclusiveMinimum":0,"examples":[500],"x-unit":"lux"},"lumens_per_bulb":{"description":"Light output of one bulb or fixture (800 lm ≈ a 60 W incandescent equivalent, 1,100 lm ≈ 75 W, 1,600 lm ≈ 100 W). Unit: lm.","type":"number","maximum":100000,"exclusiveMinimum":0,"default":800,"examples":[800],"x-unit":"lm"},"light_loss_factor":{"description":"Maintenance / utilisation factor for dirt, lamp ageing and light absorbed by walls (0.8 typical for light rooms, 0.6–0.7 for dark ones).","type":"number","minimum":0.3,"maximum":1,"default":0.8,"examples":[0.8]},"luminous_efficacy_lm_per_w":{"description":"Lumens per watt of the light source: LED 80–150, CFL 50–70, halogen 15–25, incandescent 10–17. Unit: lm/W.","type":"number","minimum":5,"maximum":300,"default":100,"examples":[100],"x-unit":"lm/W"}},"additionalProperties":false,"required":["floor_area_m2","room_type"]},"output_schema":{"type":"object","properties":{"target_lux_used":{"description":"Illuminance used for the calculation. Unit: lux.","type":"number","x-unit":"lux"},"required_lumens":{"description":"target_lux × floor_area_m2 / light_loss_factor. Unit: lm.","type":"number","x-unit":"lm"},"bulbs_needed":{"description":"required_lumens / lumens_per_bulb, rounded up.","type":"integer"},"installed_lumens":{"description":"bulbs_needed × lumens_per_bulb. Unit: lm.","type":"number","x-unit":"lm"},"total_wattage_w":{"description":"required_lumens / luminous_efficacy_lm_per_w. Unit: W.","type":"number","x-unit":"W"},"watts_per_m2":{"description":"total_wattage_w / floor_area_m2. Unit: W/m².","type":"number","x-unit":"W/m²"}}},"formula":"required_lumens = target_lux × floor_area_m2 / light_loss_factor; bulbs_needed = ceil(required_lumens / lumens_per_bulb); installed_lumens = bulbs_needed × lumens_per_bulb; total_wattage_w = required_lumens / luminous_efficacy_lm_per_w; watts_per_m2 = total_wattage_w / floor_area_m2","method":"Lumen method for uniform general lighting: illuminance (lux = lm/m²) × area gives the lumens reaching the work plane, and the light-loss factor accounts for depreciation and room absorption. Typical maintained illuminances: 100 lux circulation, 150–200 lux living, 300 lux kitchens, 500 lux desk work, 750 lux fine workshop tasks.","sources":[{"name":"Wikipedia – Lux (typical illuminance values)","url":"https://en.wikipedia.org/wiki/Lux","type":"reference","retrieved_at":"2026-09-24"},{"name":"Wikipedia – Luminous efficacy","url":"https://en.wikipedia.org/wiki/Luminous_efficacy","type":"reference","retrieved_at":"2026-09-24"},{"name":"U.S. DOE Energy Saver – Lighting Choices to Save You Money","url":"https://www.energy.gov/energysaver/lighting-choices-save-you-money","type":"government","retrieved_at":"2026-09-24"}],"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":"20 m² home office, 800 lm LED bulbs","inputs":{"floor_area_m2":20,"room_type":"home_office"},"expected":{"target_lux_used":500,"required_lumens":12500,"bulbs_needed":16,"installed_lumens":12800,"total_wattage_w":125,"watts_per_m2":6.25},"url":"https://tttkmbb.com/api/v1/calculate/room-lighting?floor_area_m2=20&room_type=home_office"},{"name":"12 m² bedroom, 470 lm bulbs at 90 lm/W","inputs":{"floor_area_m2":12,"room_type":"bedroom","lumens_per_bulb":470,"luminous_efficacy_lm_per_w":90},"expected":{"target_lux_used":100,"required_lumens":1500,"bulbs_needed":4,"total_wattage_w":16.7,"watts_per_m2":1.39},"url":"https://tttkmbb.com/api/v1/calculate/room-lighting?floor_area_m2=12&room_type=bedroom&lumens_per_bulb=470&luminous_efficacy_lm_per_w=90"}],"faq":[{"q":"Lux, lumens and watts – what is the difference?","a":"Lumens measure the light a bulb emits, lux the light landing on a surface (1 lux = 1 lm/m²), and watts the electrical power; LED efficacy (lm/W) links watts to lumens."},{"q":"Why divide by a light-loss factor?","a":"Not all emitted light reaches the work plane: dark walls absorb it, fixtures and lamps get dirty and LEDs dim with age. A factor of 0.8 adds a 25 % allowance."},{"q":"Are these lux values mandatory?","a":"No. They are typical maintained illuminances from EN 12464-1 (workplaces) and IES recommendations; homes are not regulated, and older people generally need more light."}],"tags":["lumens calculator","how many bulbs","lux to lumens","room lighting","led wattage","illuminance"],"related":[{"calculator_id":"electricity-cost","reason":"Running cost of the lights from total wattage and hours."},{"calculator_id":"circuit-load","reason":"Check the lighting circuit's breaker load."},{"calculator_id":"electric-power","reason":"Watts, volts and amps of the fixtures."}],"links":{"html":"https://tttkmbb.com/energy/room-lighting","markdown":"https://tttkmbb.com/energy/room-lighting.md","json":"https://tttkmbb.com/energy/room-lighting.json","api":"https://tttkmbb.com/api/v1/calculate/room-lighting","schema":"https://tttkmbb.com/api/v1/calculators/room-lighting","openapi":"https://tttkmbb.com/openapi.json","mcp":"https://tttkmbb.com/mcp"},"version":"v1","updated_at":"2026-09-24"},"timestamp":"2026-09-24T03:45:42Z","next_actions":[{"tool":"run_calculator","calculator_id":"room-lighting","reason":"Run Room Lighting Calculator with the inputs above."}],"links":{"markdown":"https://tttkmbb.com/energy/room-lighting.md"}}