How loud is a petrol lawnmower
Quick answer
A petrol lawnmower measures roughly 90 decibels A-weighted at a usual listening distance. That is at or above 85 dBA, where the NIOSH recommended exposure limit begins, and it allows about 2.5 hours of exposure before protection is recommended.
How loud is a petrol lawnmower compared with everything else?
Decibels are logarithmic rather than linear, which is why the numbers behave so unintuitively. An increase of 10 decibels is roughly a tenfold increase in sound intensity, and every 3 decibel increase halves how long the NIOSH recommended limit considers an exposure acceptable.
A petrol lawnmower sits at about 90 dBA, alongside city traffic from the pavement, a hair dryer, a subway train passing on the platform, a motorcycle at close range.
| Sound | Typical level (dBA) |
|---|---|
| A petrol lawnmower | 90 |
| City traffic from the pavement | 85 |
| A hair dryer | 90 |
| A subway train passing on the platform | 95 |
| A motorcycle at close range | 95 |
How long is 90 decibels safe for?
At 90 dBA the NIOSH recommended limit allows 2.5 hours, while the more permissive OSHA enforceable limit allows a longer period.
| Standard | Reference level | Exchange rate | Time allowed at this level |
|---|---|---|---|
| NIOSH recommended exposure limit | 85 dBA over 8 hours | 3 dB | 2.5 hours |
| OSHA permissible exposure limit | 90 dBA over 8 hours | 5 dB | not stated |
Common questions
- How many decibels is a petrol lawnmower?
- A petrol lawnmower is typically around 90 decibels A-weighted, measured at a usual listening distance. That figure is a representative level rather than a measurement of any particular object, and the real level changes with distance, with the enclosure the sound is in, and with the specific equipment involved. Doubling your distance from a point source reduces the level by roughly 6 decibels.
- What does A-weighted mean?
- A-weighting is a filter applied to a sound level measurement that approximates how sensitive human hearing is at different frequencies. Human hearing is far less sensitive to very low frequencies than to mid frequencies, so an unweighted measurement overstates how loud a bass heavy sound seems. Almost every figure quoted in hearing conservation is A-weighted, which is why it is written dBA.
- At what level does hearing protection become necessary?
- The NIOSH recommended exposure limit begins at 85 decibels A-weighted averaged over an eight hour day. Above that, the permissible time halves for every 3 decibel increase, so 88 dBA allows four hours and 94 dBA allows one. The separate OSHA enforceable limit begins at 90 dBA and uses a 5 decibel exchange rate, which permits considerably longer.
- Why are decibels not linear?
- The decibel is a logarithmic ratio, which is why 20 decibels is not twice 10. An increase of 10 decibels corresponds to roughly a tenfold increase in sound intensity and is usually perceived as about twice as loud. The scale is logarithmic because the range of intensities human hearing covers is enormous, and a linear scale would be unusable.
- Can I measure this myself?
- Yes, with a sound level meter, which is an inexpensive handheld instrument. A phone app gives a rough indication and is useful for deciding whether a room is obviously loud, but a phone microphone is not calibrated and its reading should not be treated as a figure. If you are measuring to decide about hearing protection at work, the measurement that matters is a time weighted average rather than a peak.
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Last updated 2026-09-17.