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

☀️

Real-Time Lux Reading

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

📷

Camera Fallback

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

📊

Min / Max Tracking

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

🌱

Perfect for Plants

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

🖥️

Workspace Ergonomics

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

🔒

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.

📅最後更新: August 2026

Prakhar Gothi

創辦人兼首席開發者, Online-Compass.com

Prakhar Gothi 是一位資深Web開發者與AI專家，在科技產業擁有超過10年的豐富經驗。憑藉在 MEMS 感測器整合、GPS 硬體以及現代Web技術方面的深厚造詣，他創立了 Online-Compass.com —— 這是一款達到航空航太級精度的導航工具，深受全球 190 多個國家使用者的信賴。

在 LinkedIn 上連結

🔬

測試與驗證方法

Online-Compass.com 上的每款工具均在 40 多款主流裝置上經過嚴格測試，包括 Samsung Galaxy S21–S24、Google Pixel 6–8、iPhone 12–15、iPad 以及多款入門級 Android 裝置。我們對照專業級導航儀器校驗感測器精度，並根據實際現場數據持續優化校準演算法。

🛡️

為什麼信任 Online-Compass.com？

擁有十年Web開發專業累積，贏得全球 190 多個國家使用者的信賴。所有感測器數據均在您的裝置本地 100% 處理——我們絕不儲存或追蹤您的位置資訊。我們的指南針元件程式碼在 GitHub 上開源，確保完全透明。每個頁面均由我們的導航技術團隊進行科學準確性審查。

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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