Room Lighting Calculator

Step-by-Step Guide

1. 1Enter Room Dimensions: Type the width and length of the room, measured wall to wall. The calculator multiplies these to get floor area before applying the lighting formula.
2. 2Select Feet or Meters: Choose the unit matching your measurement. Feet-based dimensions are converted to square meters internally since lux is defined as lumens per square meter.
3. 3Choose the Room Type: Pick from bedroom, living room, kitchen, office, bathroom, dining room, hallway, or garage for a standard lux level, or select Custom to enter your own target.
4. 4Enter Lumens per Light: Type the lumen output printed on your bulb's packaging, or apply a common LED, CFL, halogen, or incandescent preset from the bulb type panel.
5. 5Read the Fixture Count and Status: The calculator returns the number of lights needed, the lux actually achieved, and a status of under-lit, optimal, or over-lit.
6. 6Save, Copy, or Export the Result: Save the calculation to local history, copy a summary to the clipboard, or export a full text report for a lighting plan.

What This Tool Provides

• ✓Real-time recalculation as you type
• ✓8 built-in room-type lux presets plus custom lux
• ✓Quick preset rooms (bedroom, living room, kitchen, office, bathroom, garage)
• ✓Common bulb-type shortcuts (LED, CFL, halogen, incandescent)
• ✓Feet and meters unit support
• ✓Under-lit / optimal / over-lit status check
• ✓Calculation history (last 20 entries)
• ✓Export full calculation as a text report
• ✓Copy result to clipboard
• ✓Private: your inputs are not collected or stored
• ✓No signup required

Pro Tips

• 💡Always compare bulbs by lumens, never watts. An LED rated at 800 lumens produces the same brightness as a 60W incandescent that also outputs about 800 lumens, but uses roughly 85% less electricity — the wattage number tells you nothing about how bright a modern bulb actually is.
• 💡If the result comes back over-lit for a small room, don't assume you need fewer fixtures — a single bulb is often already 'too much' for a tiny space at the target lux. Add a dimmer switch instead of leaving the room permanently under-served by only one fixture.
• 💡For open-plan spaces that combine a kitchen and dining or living area, calculate each zone separately with its own lux target and sum the fixture counts, rather than averaging one lux value across the whole footprint.
• 💡Rooms with ceilings above roughly 2.4 m (8 ft) spread light over a longer throw distance before it reaches the floor. Compensate by entering a higher lumens-per-light value or targeting a higher lux level than the standard preset.
• 💡Dark walls and ceilings absorb 20–30% more light than light-colored surfaces reflect back into the room. In a room with dark paint or exposed dark wood, add one extra fixture beyond the raw calculation or move to the next brighter bulb preset.
• 💡Use Custom lux mode for anything outside standard residential or office use — retail product displays, art studios, and detailed workshop benches often need 500 lux or more, well above the built-in presets.

Common Mistakes to Avoid

• ✕Don't mix feet dimensions with a metric lux assumption without letting the calculator convert units. Lux is always lumens per square meter — entering square footage directly against a lux target overstates the required lumens by roughly 10.76×.
• ✕Don't rely on a single central ceiling fixture rated at the full lumen total. Real rooms need light distributed across multiple points to avoid dark corners and harsh shadows, even when one very bright bulb would satisfy the raw lumen math.
• ✕Don't ignore an under-lit warning because 'it looks fine during the day.' The calculator's lux target reflects evening and artificial-lighting conditions — daylight through windows isn't part of the formula and shouldn't be used to justify skipping fixtures.
• ✕Don't apply one lux standard across an entire multi-purpose room. A kitchen island needs 300 lux for food prep while an adjoining breakfast nook only needs 150 lux — treating the whole space as one zone either overlights the seating area or underlights the counter.
• ✕Don't forget to re-check the calculation after switching bulb brands. Two bulbs marketed as '60W equivalent' can differ in actual lumen output by 10–15% between manufacturers — always use the lumen figure printed on that specific product's packaging.

Standard Lux Levels by Room Type

* Standard residential and light-commercial guidelines. Specialized spaces (studios, retail displays) should use Custom lux mode.

Common Bulb Lumen Output

* LED and CFL bulbs match incandescent lumen output at a fraction of the wattage — always compare by lumens, not watts.