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Decibel (dB) Meter

A live sound-level meter that reads your microphone in real time, with a big level readout, peak hold, fast/slow response, a running average (Leq), and clip detection.

ℹ This reads relative dBFS, not calibrated dB SPL. A web browser can’t know your microphone’s real-world sensitivity, and phone/laptop mics apply automatic gain — so the numbers are relative (great for comparing "louder vs quieter" and spotting clipping), not a true environmental decibel reading. For real dB SPL (e.g. workplace noise), use a calibrated sound-level meter. Nothing is recorded or uploaded.

Microphone

Idle — press Start.

Response

Fast (~125 ms) follows transients; Slow (~1 s) gives a steadier reading. Approximate.

Level

—dBFS
Peak — dBFS
-60-48-36-24-120
Set an offset (using a known reference) to estimate dB SPL.
Peak (max)
—
Average (Leq)
—
Clips
0
Elapsed
0:00

Understanding the Reading

This meter shows level in dBFS — decibels relative to digital full scale. 0 dBFS is the loudest signal your audio system can capture without clipping; everything quieter is a negative number (a quiet room might read around −50 to −40 dBFS, normal speech up close perhaps −20 to −12 dBFS, with peaks approaching 0). That’s the opposite of environmental decibels (dB SPL), where louder is a bigger positive number.

The big number is a smoothed RMS level (average energy), which is what tracks perceived loudness. Peak is the highest instantaneous sample — useful for catching clipping that the average hides. Average (Leq) is the equivalent continuous level since you pressed Start, and Clips counts how many times the signal hit the ceiling (a sign your input gain is too high).

Why it isn’t calibrated dB SPL

A true sound-level meter is calibrated so that a known acoustic pressure produces a known reading. A browser only receives a normalized digital signal — it has no idea how sensitive your mic is, how far you are from the source, or how much automatic gain control the OS applied. So dBFS here is relative: excellent for comparisons ("is this louder than that?", "am I clipping?"), useless as an absolute "this room is 72 dB" claim. The optional offset lets you roughly shift the scale if you calibrate against a real meter, but it’s still an estimate.

Frequently Asked Questions

Why are the numbers negative?
Because this is dBFS, where 0 is the digital maximum and quieter sounds are negative. A reading of −30 dBFS is quieter than −10 dBFS. Environmental meters (dB SPL) use positive numbers that grow with loudness — a different scale.
Can I use this to measure room or workplace noise in dB?
Not as an absolute figure. A browser mic isn’t calibrated and the OS often applies automatic gain, so it can’t give a trustworthy dB SPL value. Use it for relative comparisons and clip checking; for compliance or real measurements use a calibrated sound-level meter.
What does the calibration offset do?
It simply adds a fixed number of decibels to the reading. If you have a real SPL meter, you can note the difference between it and this tool at one level and enter that as the offset to roughly align them. Without a reference it’s just a guess, so it’s off by default.
What’s the difference between RMS and peak?
RMS is the average energy over a short window and tracks how loud something sounds. Peak is the single highest sample and catches brief spikes. Peak is always equal to or higher than RMS; the gap between them is roughly the signal’s crest factor.
What is Leq?
The equivalent continuous level — the steady level that would carry the same total energy as the varying sound since you started. It’s how noise exposure is usually summarized. Here it’s in dBFS, so again relative, not absolute.
Fast or Slow response — which should I use?
Fast (~125 ms) reacts quickly and is good for catching transients and seeing detail. Slow (~1 s) averages more and is steadier, better for reading a typical level without the number jumping around. They’re approximate emulations of the classic meter settings.
Is my audio recorded?
No. The microphone signal is analyzed in real time to compute the level and is never recorded, saved, or transmitted. The mic is released when you press Stop or close the tab.

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Pitch Detector
Find the pitch of any sound in real time.
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