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Lumens measure how much visible light a source emits; lux measures how much light reaches a given area. One lux equals one lumen per square meter. A bulb’s lumen rating therefore cannot, by itself, tell you how brightly a desk, floor, or wall will be lit.
What do lumens and lux measure?
Lumens measure a source’s total light output
A lumen (lm) is the unit of luminous flux: the total visible-light output of a source. It describes the light emitted, not how much reaches a particular point in a room. The NIST Guide to the SI lists the lumen as the unit for luminous flux.
Lux measures light arriving on an area
A lux (lx) is the unit of illuminance, or luminous flux per unit area. One lux is one lumen per square meter (lm/m²), as defined in the NIST glossary entry for lux.
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#1 Best Overall
- Measures luminosity from 0 to 200,000 Lux and ambient temperature
- High accuracy of ±3% rdg ± 8 dgts (10,000 Lux)
- 4 digital color LCD screen, MIN/Max readings, data hold, auto power off, and low battery indication
- Wide range of application, use lux light meter for set design, factory, office or home use
- lightweight and compact, 2 years long period warranty
How do lumens relate to lux?
The units are related, but there is no single conversion from a lamp’s lumens to the lux at every location. Lux is lumen output distributed over an area: if the same amount of light were spread evenly over a larger area, illuminance would be lower. In a real room, the result also depends on how the fixture directs light, its distance from the target, and how room surfaces reflect or absorb it.
For example, a bulb’s lumen figure describes its total output. It does not establish the lux on a desk below it. A lux reading is meaningful only for the location and surface where it was taken.
Rank #2
- High Precision & Fast Response: This high-precision illuminance meter delivers lightning-fast readings 2 times per second, ensuring you get accurate light intensity data—perfect for creating the ideal growing environment for your plants.
- FC/LUX Conversion: FC or LUX? The Power is in Your Hands! Effortlessly toggle between FC and LUX to measure light intensity in the unit that suits your gardening needs—precision made simple.
- PEAK Data Recording: Instantly lock in and display the highest light pulse value with a single press of the PEAK button—perfect for measuring lightning, laser beams, and other brief high-intensity sources.
- Low Battery Alert: Stay powered, stay prepared! A handy + - symbol appears when the battery runs low, so you’ll always know when it’s time to swap out the 9V battery and keep your light measurements going strong.
- Versatile Usage: Ready for any setting! Whether indoors or outdoors, this meter is perfect for homes, offices, factories, or measuring sunlight intensity to create the perfect environment for your plants to thrive.
Which measurement should you use?
| What you want to know | Use | What it tells you |
|---|---|---|
| How much visible light a lamp emits | Lumens (lm) | The source’s total luminous flux |
| How much light reaches a desk, floor, or other defined area | Lux (lx) | Illuminance at that area; 1 lx = 1 lm/m² |
When comparing bulbs, use lumen ratings to compare stated total output. To compare how well fixtures light a particular work surface, consider their light distribution and mounting position, then measure lux at the same target surface under comparable conditions. Color temperature and color rendering can help with other lighting choices, but they do not substitute for either lumen output or illuminance.
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How do you measure lux in a room?
Use a lux meter to check illuminance at a defined spot. The meter measures the light arriving at its sensor; it does not directly measure a lamp’s total lumen output. For a useful comparison, keep the target location and sensor position consistent, and note where the reading was taken rather than treating it as a room-wide value.
Rank #3
- ☀【HIGH ACCURACY】+/- 4% of readings for 10000 Lux, 1000 FC; +/- 5% of readings +/- 10 digits for 400000 Lux, 40000FC
- ☀【0.4 SECOND RESPONSE】2~3 times sampling per second, Instantly to measure out how much luminosity intensity you’re getting, No more guessing
- ☀【WIDE MEASURE RANGE】 This light meter can measure luminance at 0.01~400,000 Lumens, (0.01~40,000 Foot Candles), Which is much wider than the others. Resolution 0.01
- ☀【EASY TO USE】The light sensor can be rotated 270º, so you don’t need to turn around the light meter to measure luminosity intensity from different angles. Just rotate the sensor, and you can still read the illuminance at front
- ☀【MEMORIZE THE LIGHT READINGS】This Lux Meter can help you record 33 sets of readings,Temp Testing, The RELATIVE measuring mode will show you the difference between current / recorded data. Ideal lux meter to measure light intensity for LED grow lights,garden, plants, school, office, state, LED lights, indoor and outdoor
- Choose the surface or location you want to assess, such as a desk or plant area.
- Place the lux meter’s sensor at that location and orient it toward the incoming light.
- Record the reading and the sensor position. Repeat at other locations if you need to understand how illumination varies across the room.
NIST lists illuminance among the quantities covered by its photometric calibration services and describes photometric measurement methods for solid-state lighting products in its measurement guidance.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How are lux and other lighting terms different?
Lux is illuminance, not a synonym for brightness in every context. “Brightness” may describe a person’s subjective impression or refer informally to different measured properties. Candela measures luminous intensity, while luminance is expressed in candela per square meter. These quantities describe different aspects of light and are not interchangeable with lumens or lux.
Quick Recap
Best Value
- Lighting accuracy: plus or minus 3% plus or minus 10 dgts (10000 LUX)
- EXTRA LARGE RANGE Our digital illuminance meter has a wide measuring range of up to 200,000 LUX. The highly sensitive illuminance sensor ensures accurate and fast response with a sampling frequency of up to 2 times per second.
- User-friendly design: Easily switch between the two main units of illumination intensity - LUX and FC - as needed. The LCD display ensures clear vision, the backlight ensures the readability of the meter even in dark environments.
- Multifunctional: With our meter, you can not only measure the current brightness, but also the maximum and minimum values. With the data hold function, you can freeze the reading on the display, which can be useful when you need to record the measurement.
- ENERGY EFFICIENT The meter has an automatic shut-off function which helps to save battery when not in use. A low battery indicator lets you know when it's time to change the battery so that the meter is always ready to use.
Rank #4
- ✅【High Accuracy】DANOPLUS Light Lux Meter is equipped with high-tech sensor, the accuracy of lux reading is +/-4% +/-10dgts; 400~700nm spectral range
- ✅【Auto Range Setting】This light meter is designed with 4 lux ranges setting, 200/2,000/20,000/200,000, and 0 to 20,000 foot candles(FC) unit Switchable
- ✅【360 Degree Rotating Sensor】DANOPLUS Light Meter is equipped with 360 degree rotating sensor, which separate with the light meter, can adjust suitable position to ensure the accurate measurement
- ✅【Multi-Fuctional】MIN/MAX readings, Data Hold, Auto Power Off&Disable Auto Power Off, Auto Range Selection and Low Battery Indication
- ✅【Wide Application】This compact Light Meter is used for measuring the brightness of visible light (400~700nm spectral range), it's suitable for factories, hospitals, schools, home, office, etc.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
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