Online Decibel Meter
Guide & FAQ- dBFS
Values in dBFS: 0 is the loudest the microphone can record, quieter sounds are negative. Minimum, average and maximum are since the last reset.
About the dB SPL estimate
Uncalibrated, approximate. A browser measures the signal level of the microphone in dBFS. It cannot know how sensitive your microphone is or what automatic processing your device applies, so the dB SPL figure is only a rough guide (often 5 to 15 dB off). Do not use it for health, safety, legal or workplace noise measurements; use a calibrated sound level meter for that.
To calibrate, play a steady sound next to a reference meter, enter its reading, and press Set. The offset is remembered in this browser.
Guide: Online Decibel Meter
How to measure sound level
Press Start measuring and allow the microphone when the browser asks. The big number shows the current level in dBFS and an approximate dB SPL below it. The bar and the history graph move with the sound, and the grid shows minimum, average, maximum and a three-second peak hold.
Understanding the numbers
- dBFS is the exact signal level in your device: 0 is the maximum, quiet rooms read around minus 70 to minus 50.
- dB SPL is real-world loudness. Normal conversation is about 60 dB SPL, a busy street 80 dB, a rock concert 110 dB.
- Every 10 dB sounds roughly twice as loud, and every 3 dB doubles the sound energy.
Be honest about accuracy
The SPL estimate is uncalibrated and approximate. Use the calibration box with a real meter to improve it, and never rely on it for hearing protection, workplace or legal noise limits.
Privacy
The microphone is only opened after you click Start, the sound is analysed live in your browser, and nothing is recorded or sent anywhere.
FAQ
How accurate is this decibel meter?
It measures the microphone signal accurately in dBFS (decibels relative to digital full scale), but turning that into dB SPL, the real loudness of the air, needs the sensitivity of your microphone, which a web page cannot know. The SPL figure is an estimate using an adjustable offset and can be 5 to 15 dB off. It is fine for comparing sounds and for a rough idea, not for official measurements.
What is dBFS?
dBFS means decibels relative to full scale. 0 dBFS is the loudest level the microphone and device can record; everything quieter is negative, for example minus 40 dBFS. Higher (closer to zero) means louder.
How can I calibrate it?
Play a steady sound, read it on a real sound level meter, type that reading into the calibration box and press Set. The offset is stored in your browser, so the estimate follows your microphone. Calibrate near the level you plan to measure, because microphones are not perfectly linear.
Why do readings change between devices?
Every microphone has a different sensitivity, and many phones and laptops process the signal. The tool asks the browser to switch off echo cancellation, noise suppression and automatic gain control, but some devices ignore that.
What is peak hold?
Peak hold shows the loudest instant peak of the last three seconds, so short clicks and bangs do not disappear before you can read them.
Does the tool record or upload sound?
No. The microphone signal is analysed in your browser as it arrives. Nothing is recorded, saved or sent, and the microphone is released when you press Stop.