Enrichment · Passion Projects · Home and garden

Buy bulbs by the lumen,
room by room.

List the rooms with their size and use. The calculator gives the lumens each one needs, the bulbs to buy at the number on the box, and what the light costs a year with LEDs against old bulbs.

Plan the lightingWhat you get

The lighting calculator

The worked example is a made-up two-bedroom apartment. Nothing you type leaves this browser.

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What you get

Enrichment · Passion ProjectsFree

What you finish with
Lumens and bulbs for each room and the whole home, LED watts, yearly kWh and cost, and the incandescent comparison. It prints as a shopping summary and downloads as a spreadsheet.
Who it is for
Families and students furnishing a home or a first apartment, family and consumer sciences classes, and anyone switching to LED.
Format
Browser calculator for a phone, tablet or computer, by touch or keyboard. Prints a summary; downloads a spreadsheet (.csv); export and import a file.
Access
Free. No account, no sign-in and nothing to install. Everything you type stays in this browser; nothing is sent to Caveat.
Where it lives
The Passion Projects space in Caveat Enrichment.
Support
Questions, a correction or a request: team@caveatacademic.com.

How to use it

  1. Measure each room’s length and width.
  2. Pick the use, adding a task line for counters or a desk.
  3. Type the lumens and lumens per watt from the bulb box.
  4. Type the hours the lights are on and your electricity price.
  5. Print the bulb count for the store.

Plan the lighting

How the light is planned

Area times a planning range, then bulbs by the lumen.

The worked example: the kitchen in a two-bedroom apartmentKitchen floor120 sq ft12 × 10 ftLumens4,200120 × 35 lm per sq ftBulbs64,200 ÷ 800, round upWhole home22 bulbs196 W of LEDThe worked example: the kitchen in a two-bedroom apartmentKitchen floor120 sq ft12 × 10 ftLumens4,200120 × 35 lm per sq ftBulbs64,200 ÷ 800, round upWhole home22 bulbs196 W of LED
Light is planned in lumens per square foot; bulbs are counted in lumens, never in watts.

Lumens, not watts

Lumens measure light; watts measure the power drawn. An LED that gives 800 lumens, the light of an old 60-watt bulb, draws about 8 to 10 watts. The Lighting Facts label on every box lists the lumens, the watts and the colour temperature, so compare bulbs by lumens.

Planning ranges

A lumen spread over one square foot is a footcandle. Living rooms and bedrooms are comfortable around 10 to 20 lumens per square foot, kitchens around 30 to 40, and counters, vanities and desks closer to 50 to 80 where you read or cut. These are starting points: dark paint, tall ceilings, lampshades and older eyes all call for more.

Sources

  1. U.S. Department of Energy, Energy Saver. Lumens and the Lighting Facts label; choosing LED lighting (energy.gov/energysaver).
  2. Federal Trade Commission. Lighting Facts label for light bulbs (ftc.gov).
  3. ENERGY STAR. Light bulbs: lumens and watt equivalents (energystar.gov).
  4. Illuminating Engineering Society. Lighting Handbook, recommended illuminance for residential tasks (ies.org).

The worked example is made up. Planning ranges are general guidance, not a building code. Your entries stay in this browser. Support: team@caveatacademic.com.