Illuminance Tool

Online Light Meter & Lux Sensor

Measure light intensity (lux) instantly using your device's ambient light sensor or camera. Perfect for photography, indoor plants, and workspace ergonomics.

--lx

Very Dark

Min Lux--

Max Lux--

Hold your device flat, facing the light source. Values update in real-time based on your environment.

Hold your device facing the light source. Values update in real-time. If the ambient light sensor is blocked, the camera fallback provides an estimate.

Why Measure Light in Lux?

Lux is the standard unit of illuminance, measuring how much luminous flux is spread over a given area. Whether you are setting up a home office, nurturing indoor plants, or fine-tuning exposure for photography, understanding the exact light intensity is crucial.

Historically, measuring lux required dedicated handheld light meters. Today, almost every modern smartphone, tablet, and laptop contains an Ambient Light Sensor (ALS)—originally designed to auto-adjust your screen brightness. This tool taps directly into that hardware via the W3C Generic Sensor API, turning your device into an instant, free light meter.

Features & Capabilities

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Real-Time Lux Reading

Live, instant updates directly from your device hardware. See exact lux values as you move around.

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Camera Fallback

If your browser blocks the Ambient Light API, the tool seamlessly falls back to a camera-based brightness approximation.

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Min / Max Tracking

Automatically tracks the lowest and highest light levels during your session to help you gauge light variation.

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Perfect for Plants

Easily determine if your Monstera is getting enough indirect sunlight or if your succulents need a brighter window.

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Workspace Ergonomics

Ensure your office meets the recommended 300-500 lux for reading and computer work to reduce eye strain.

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100% Privacy-Safe

All light and camera processing happens locally on your device. We do not store or transmit any sensor data.

How to Use the Light Meter

Grant Permissions

Allow the browser to access your device's sensors. If prompted for camera access (fallback mode), grant it for accurate approximations.

Position the Device

Place your phone or laptop exactly where you want to measure the light. Ensure your hand or shadow isn't blocking the front-facing sensor.

Read the Lux

Look at the live lux value. Values below 50 indicate dim lighting, while direct sunlight can exceed 10,000 lux.

📅Last Updated: August 2026

Prakhar Gothi

Founder & Lead Developer, Online-Compass.com

Prakhar Gothi is a seasoned Web Developer and AI Expert with over 10 years of experience in the tech industry. His deep expertise in MEMS sensor integration, GPS hardware, and modern web technologies led to the creation of Online-Compass.com — an aerospace-grade navigational tool trusted by users in 190+ countries.

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How We Tested

Every tool on Online-Compass.com is rigorously tested on 40+ device models including Samsung Galaxy S21–S24, Google Pixel 6–8, iPhone 12–15, iPad, and various budget Android devices. We verify sensor accuracy against professional-grade navigation instruments and continuously update our calibration algorithms based on real-world field data.

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Why Trust Online-Compass.com?

Backed by a decade of web development expertise and trusted by users across 190+ countries. All sensor data is processed 100% locally on your device — we never store or track your location. Our compass widget code is open-source on GitHub for full transparency. Every page is reviewed by our navigation technology team for scientific accuracy.

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Frequently Asked Questions

How accurate is this online light meter?

The accuracy depends entirely on your device's hardware. Most modern smartphones have highly sensitive ambient light sensors that provide very reliable lux readings for everyday tasks like indoor lighting assessment and plant care.

Why does the tool ask for camera permissions?

Not all browsers (especially iOS Safari) allow access to the native Ambient Light Sensor API. If the API is blocked, our tool uses your device's camera to analyze the average brightness of the video feed and mathematically estimates the lux value. This fallback is a safe approximation and runs entirely offline.

How many lux do my indoor plants need?

Low-light plants (like Snake Plants) survive in 500–2,500 lux. Medium-light plants (like Philodendrons) prefer 2,500–10,000 lux. High-light plants (like Succulents) thrive in 10,000+ lux (direct sunlight).

Try every Online-Compass tool — free, no install.

All tools run entirely inside your browser using your phone's MEMS sensors, GPS, and magnetometer. No app store. No account. No tracking.

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Light Meter & Lux Sensor - Measure Illuminance Online - Online Compass