dB Power Ratio Calculator

Enter TWO Power values,
(use same units for both: Kilowatts, Watts
Milliwatts etc.) then click CALC.
Power 1 (output) Power 2 (input)
Decibels (dB) =
Formula used: dB = 10 log10 ( Power 1 / Power 2 ) 1 Bel = 10 decibels (dB)

dB Voltage Ratio Calculator

Enter TWO Voltage values,
(use same units for both: Kilovolts, Volts,
Millivolts etc.) then click CALC.
Voltage 1 (output) Voltage 2 (input)
Decibels (dB) =
Formula used: dB = 20 log10 ( Voltage 1 / Voltage 2 ) 1 Bel = 10 decibels (dB)


The decibel (dB) is a unitless measurement for expressing ratios.  Using 
the logarithm allows very large or very small ratios to be represented with
a small number for convenience.  Common scientific notation is very similar.
dB is a dimensionless unit, a pure number without a proper unit like feet, 
pounds or seconds.  Decibels are useful for a wide variety of measurements
especially in acoustics, but also in physics, electronics and other 

When used to compare a variable quantity to a known reference quantity, the 
measurement is qualified with a suffix. For example, "dBm" indicates that 
the reference quantity is one milliwatt.

The bel (B) is mostly used in telecommunication, electronics, and acoustics. 
Invented by engineers of the Bell Telephone Laboratory to quantify the 
reduction in audio level over a 1 mile (1.6 km) length of standard telephone 
cable, it was originally called the transmission unit or TU, but was renamed 
in 1923 or 1924 in honor of the laboratory's founder and telecommunications 
pioneer Alexander Graham Bell.

The bel was too large for everyday use, so the decibel (dB), equal to 0.1
bel (B), became more commonly used. The bel is still used to represent noise 
power levels in hard drive specifications, for instance.  Our ears and eyes 
both respond logarithmically to acoustic power and luminosity respectively.

Alexander Graham Bell (18471922) was a Scottish scientist, inventor, and 
innovator. He immigrated to Canada in 1870 and then to the United States 
in 1871, a month after he turned 24.

On 1876 February 14 Bell's telephone patent application is filed at the 
United States Patent Office.  On March 7 United States Patent No. 174,465
is officially issued for Bell's telephone.

Website by Jim Shook 03/31/2007