This decibel meter uses your device's microphone to estimate the sound level around you. Press Start the decibel meter and allow the microphone. The large number is the live level in dBA. For a fair figure, let it run for at least a minute and read the Leq, the true average over the whole session. Without calibration, treat the numbers as an estimate.
How to take a good reading
- Keep Processing off. Noise suppression and automatic gain change the level and make readings meaningless.
- Hold the phone or laptop at arm's length, microphone pointing at the noise, away from your body and clothing.
- Stay still and quiet yourself. Your own voice and handling noise count as sound.
- Measure for at least a minute, longer if the noise comes and goes. Read Leq for the average, Max for the loudest moment, and L90 for the background.
- Outdoors, shield the microphone from wind. Wind on a bare microphone reads as loud, low noise.
What each number means
| Reading | What it tells you |
|---|---|
| Live level | The level right now, smoothed with the Fast (0.125 s) or Slow (1 s) time weighting. |
| Leq (average) | The steady level with the same total sound energy as the whole session. The most useful single number, and the one hearing limits are based on. |
| Max and Min | The highest and lowest Fast-weighted level since you started. |
| Peak (Z) | The highest instantaneous level, unweighted. It reacts to claps and bangs that the time-weighted level smooths out. |
| L10, L50, L90 | The level exceeded 10%, 50% and 90% of the time. L90 is the background; a big gap between L10 and L90 means the noise comes in bursts. |
| Daily time at this level | How long a day you could spend at the current A-weighted Slow level before reaching the NIOSH or OSHA limit. |
| Session dose | How much of a full day's allowed noise this session has used so far. 100% is the limit. |
dBA, dBC or dBZ?
dBA turns down low and very high frequencies, roughly as your ears do at moderate levels. Use it for almost everything, including hearing safety, because NIOSH and OSHA limits are set in dBA. dBC is much flatter and keeps the bass, so a big gap between dBC and dBA means low-frequency noise such as traffic rumble, music bass or machinery. dBZ is unweighted. The weightings follow the formulas in IEC 61672-1, the international sound level meter standard. See what is a decibel for the curves.
Fast or Slow?
Fast (0.125 s) follows quick changes, such as speech or a passing car. Slow (1 s) steadies the number for noise that fluctuates, and it is the response OSHA specifies for its limits. The Leq average is the same either way.
How accurate is it?
Phone and laptop microphones were made for voices, not measurement. Each model has a different sensitivity, and many cut low bass or clip on loud sounds. A browser measures the signal in dBFS (decibels relative to the loudest digital value) and needs an offset to turn that into decibels of sound pressure. Until you calibrate, we use a typical offset, so readings can be off by 10 dB or more.
NIOSH researchers Kardous and Shaw tested smartphone sound apps against a professional meter in 2014. Only a few iOS apps came within ±2 dB of the reference. Their follow-up study found that external microphones you can calibrate give much closer results. This meter is not a Class 1 or Class 2 sound level meter. Do not use it for legal, workplace-compliance or noise-complaint evidence.
Calibrating this meter
If you can borrow a real sound level meter, open Calibration under the meter. Play a steady noise, such as pink noise from our speaker test. Set both meters to dBA and Slow, hold them side by side, type the real meter's reading, and press Match. The offset is saved in this browser for this microphone and used again next time, including by the classroom noise meter. A different microphone or browser needs its own calibration.
How long can I stay at this level?
NIOSH recommends no more than 85 dBA averaged over an 8-hour day, halving the time for every 3 dBA more. OSHA's legal limit for US workplaces is 90 dBA for 8 hours, halving for every 5 dBA, and it requires a hearing conservation program from an 8-hour average of 85 dBA. Use the noise exposure calculator to work out a whole day. The decibel chart shows the time limit at each level.
Downloading your data
Download CSV saves one row per second: Leq and Fast maximum in A, C and Z weighting, already including your calibration offset. It opens in Excel, Google Sheets or Numbers. Nothing is sent anywhere; the file is created in your browser.
Common questions
Is an online decibel meter accurate?
Only roughly, unless you calibrate it. Phone and laptop microphones differ by model, so an uncalibrated reading can be off by 10 dB or more. Calibrating against a real sound level meter makes it much closer, but it is still not a certified instrument.
Does it work on iPhone and Android?
It is built for Safari on iPhone and Chrome on Android, with no app to install. Allow the microphone when asked. Some phones still apply their own processing, so calibration matters even more on mobile.
Can it measure how loud my headphones are?
No. A microphone measures the room, not the sound inside your ears from headphones. iPhone and many Android phones have their own headphone level features for that.
Why does it read differently from my phone's decibel app?
Each app uses its own offset for your microphone. Calibrate both against the same real meter, or compare changes (louder or quieter) rather than absolute numbers.
Is my sound recorded?
No. The meter measures levels in your browser and keeps only the numbers. Nothing is saved or uploaded unless you download the CSV yourself.
What is a normal decibel level for a room?
NIDCD lists normal conversation at 60–70 dBA. A quiet room is lower; measure yours and read the L90 for the background level.
Last reviewed 14 November 2026 by Sri Murugan Systems. Found a mistake? Tell us.