dB Converter

Knowledge Base

Why There Are So Many Different "dB" Units

dB is always a ratio, never an absolute unit on its own, dBu and dBV differ only in what voltage they treat as their 0 dB reference point (0.775V and 1V respectively), which is why the same real-world voltage gives a different-looking number in each. dBFS is different again: it's relative to a digital system's maximum representable value, with no fixed voltage meaning until you calibrate it against real analog gear.

Why +4 dBu and -10 dBV Exist

+4 dBu became the standard reference for professional balanced audio gear. -10 dBV became the standard for consumer and prosumer unbalanced gear. This is also why connecting professional and consumer-level gear directly can introduce noise or level mismatches without a proper interface between them.

dBFS Calibration Is Convention, Not Physics

Unlike dBu/dBV (fixed by definition), a digital system's 0 dBFS has no inherent real-world voltage until a manufacturer or engineer calibrates it to one, different studios and equipment manufacturers have historically used different calibration points, which is why this tool asks you to pick a reference rather than assuming one universal answer.

FAQ

Q: Why does my interface's meters show a different dBFS than my outboard gear's dBu meter for the same signal?
A: They're likely calibrated to different reference points. Check your interface's specific calibration documentation rather than assuming a universal standard applies.

Q: What's a "linear gain ratio"?
A: The plain multiplication factor a signal is scaled by. A gain ratio of 2 doubles voltage (a +6.02 dB change). A ratio of 0.5 halves it (a −6.02 dB change).

Worked examples: common levels across every scale

The levels you meet most often in audio equipment, converted between all four scales at once. Zero dBu is 0.7746 volts, the reference every dBu figure is measured against.

Plus four dBu is the nominal operating level of professional equipment, and minus ten dBV is the consumer equivalent. The gap between them is close to twelve decibels, which is why plugging consumer gear into professional inputs sounds quiet and doing the reverse distorts.

Vocabulary

Decibel. A ratio between two levels expressed on a logarithmic scale, not an absolute amount. Every 6 dB roughly doubles or halves the voltage, and every 20 dB multiplies or divides it by ten.

dBu. Decibels measured against a reference of 0.7746 volts, the voltage that delivers one milliwatt into a 600 ohm load. The standard scale for professional audio equipment.

dBV. Decibels measured against a reference of 1 volt. Common on consumer equipment. A dBV figure is always about 2.2 dB lower than the same voltage expressed in dBu.

Nominal level. The level a piece of equipment expects to see at its input for normal operation. Professional gear runs at +4 dBu, consumer gear at -10 dBV, and mismatching the two costs either headroom or signal to noise.