Compare Room Lighting With a Lux Target You Supply — Free
Lighting labels provide lumens; a room plan starts with area. Multiply area by a target illuminance you selected, subtract the fixture output you entered and expose a rough lumen gap without pretending to design the room.
The proof surface
Colour-contrast tools compare foreground and background colours. This docket compares a user-entered room-area target with the total lumen figure supplied for current fixtures; it does not test glare, distribution or visual comfort.
Why the flat version breaks
Using watts as lumens
Electrical input power and luminous output are different quantities; keep the units in the labels.
Double-counting fixtures across zones
Assign each fixture to the zone it actually illuminates.
Treating the gap as a fixture count
A lumen shortfall is not a purchase recommendation or room-lighting design.
How to work the room-light output docket
Use the area you intend to illuminate, not necessarily the whole room. Split zones if they have different tasks or fixture arrangements.
Lux is lumens per square metre. Choose the target from a lighting plan, task requirement or qualified designer; this tool supplies no recommended target.
Use the stated output for the fixtures in that zone. The arithmetic is area × target lux minus current lumens, with a negative gap shown as zero shortfall.
Fixture placement, optics, dimming, daylight, surface reflectance and user needs all matter. A lumen total cannot tell you where a light should go.
What the room-light output docket replaces
| Question | Before | Visible working |
|---|---|---|
| Using watts as lumens | Electrical input power and luminous output are different quantities; keep the units in the labels. | Enter a target from your own source |
| Double-counting fixtures across zones | Assign each fixture to the zone it actually illuminates. | Add the fixture lumen values |
| Treating the gap as a fixture count | A lumen shortfall is not a purchase recommendation or room-lighting design. | Treat a positive gap as a question, not a prescription |
A local arithmetic aid replaces hand calculation, not expert review. No paid AI service is needed.
Run it on the samples, right here
FIRST-LOAD
Input is processed locally and a draft is saved automatically in this browser profile when storage is available. Reset to sample clears that draft; Pro history has its own clear button. A state link encodes your inputs in its URL: share only non-sensitive rows. Browser history, clipboard and anyone receiving the link may retain it. Optional AI use below leaves this device; it is not required.
Unit arithmetic only, not electrical, visual-health or building-code advice. This does not certify a lighting level or accessibility. Ask a qualified lighting professional and follow product installation instructions before changing fixtures or wiring.
Data note: Everything runs in this browser tab on the room-light output docket: your room | floor area m² | current fixture lumens stays on this device, nothing is uploaded, and the reading is rebuilt only when you press run.
Go deeper: the companion app files the same reading as a clerk's docket sheet
The article demo above runs without limits. The companion app keeps a local history, exports the rows as CSV, prints the room-light output docket reading, and holds your drafts on this device — one free run, then $ 4 one-time for the layer that keeps filing.
The room-light output docket reading is complete for free. The optional $4 layer adds print, row CSV and the last five local reading summaries; it does not add hidden answers. Checkout is not configured yet; the article demo remains unlimited.
Open the compare room lighting with a lux target you supply companionBoundary
Unit arithmetic only, not electrical, visual-health or building-code advice. This does not certify a lighting level or accessibility. Ask a qualified lighting professional and follow product installation instructions before changing fixtures or wiring.
What this is built on
- Method: the equation is stated next to the result and uses only quantities entered by the reader.
- All sample records are invented examples. No standard, tariff, product rate, schedule or policy is fetched or represented as verified.
- For any threshold or rule, use the current value from the provider, handbook or qualified professional responsible for it.
Before: Electrical input power and luminous output are different quantities; keep the units in the labels. After: the room-light output docket shows the working beside each named row so the reader can change the assumption and inspect the consequence.
Optional AI formatting, not calculation
For this room-light output docket, an external AI text tool may help format non-sensitive notes if you already use one. No AI service or account is required: manual entry completes the same free core calculation. Do not paste private or sensitive data. Review every value against the source before using it.
Format my non-sensitive notes for a room-light output docket. Return plain rows only: room | floor area m² | current fixture lumens. Preserve supplied quantities exactly. Do not guess missing values; list questions separately. Do not calculate or add advice. I will check every row before pasting into the local tool.
Accepted schema: room | floor area m² | current fixture lumens. No AI response is executed as code.
Walk three labelled examples
First reading. The invented sample Desk room | 12 | 1800 uses chosen target illuminance in lux = 200. The displayed total lumen shortfall is 600.00000 lumens short. Follow the row note back to the measurements and conversion rather than treating the headline number as a recommendation. The sample is deliberately concrete so the reader can reproduce the arithmetic by hand.
Changed assumption. The alternate input Kitchen zone | 15 | 4000 produces 0.00000 lumens short for the displayed summary. Compare it with the first reading to see which entered quantity moves the result. In a real plan, change only the assumption that has a traceable source; do not tune a value just to make a row pass.
Boundary case. With Small room at target | 10 | 2000 and the same setting, the worked result is 0.00000 lumens short. This case shows how the arithmetic behaves at a useful edge, not that the underlying process has been measured or verified. Check the boundary statement beside the result and confirm any consequential input with the responsible person before acting.