Decibel meter: Accuracy limits

Browser microphones are not calibrated sound-level meters. Use the readings for comparison and training only. Do not use them for legal, medical, or compliance decisions.

Free to use
Runs on this device
No account

Procedure

Allow microphone access. Keep the device still. Prevent handling noise.
Keep the same device position, browser, and input settings for each comparison.
Set the calibration offset against a trusted reference meter. Then read the current, average, and peak values.

What the reading means

An uncalibrated microphone gives a relative digital level. The displayed estimate includes your saved offset. It is not an IEC 61672 measurement or a verified dBA value.

Browser support

Use a current version of Safari, Chrome, Edge, or Firefox. Microphone tools require HTTPS and microphone permission.

How the browser decibel estimate is calculated

Where supported, the site disables echo cancellation, noise suppression, and automatic gain control. It removes the sample mean, calculates RMS amplitude, converts the value with 20 × log10(RMS), and adds the saved calibration offset.

Current is the latest estimate. Average is a five-second energy average. Peak is the highest estimate since Start. No A- or C-weighting is applied. An uncalibrated result is not a physical SPL measurement.

Method reviewed 30 July 2026

Calibrate for this device

Put this device next to a trusted reference meter. Point both at the same steady source.
Prevent wind, handling noise, clipping, and microphone movement.
Adjust the offset until the readings agree. Keep the same device, browser, and input configuration.

Technical sources

MDN getUserMedia()NIOSH Sound Level Meter App W3C Web Audio API IEC 61672-1