dB ↔ Linear Unit Converter
The following calculators handle both sides of the bench: conducted quantities measured at a port or cable, and radiated free-space field strength. Pick the system you're working in below.
Voltage, current, and power at a port or along a cable.
V ↔ dBμV
A ↔ dBμA
mW ↔ dBm
Field strength and power density of a plane wave in free space.
V/m ↔ dBμV/m
A/m ↔ dBμA/m
T ↔ dBpT
W/m² ↔ dBm/m²
Convert the quantities you measure at a connector, LISN, or cable: voltage (V ↔ dBµV), current (A ↔ dBµA), and power (mW ↔ dBm). These are the units behind most conducted-emission and conducted-immunity limits.
Convert plane-wave field quantities: electric field (V/m ↔ dBµV/m), magnetic field (A/m ↔ dBµA/m), magnetic flux density (T ↔ dBpT), and power density (W/m² ↔ dBm/m²). These are the units used for radiated-emission limits and field-strength measurements.
Which reference units are used
Decibel units are always relative to a fixed reference: dBµV to 1 µV, dBµA to 1 µA, dBpT to 1pT, dBm to 1mW, and dBm/m² to 1mW/m². Field and amplitude quantities (voltage, current, E-field, H-field, flux density) use 20·log₁₀, because they scale with the square root of power; power and power-density quantities use 10·log₁₀. Mixing up the factor of two is the single most common decibel error in EMC work.
Frequently asked questions
How do I convert dBµV to volts?
V=1µV×10^(dBµV/20). For example, 120dBµV=1V. The conducted calculator does this in both directions automatically.
What's the difference between dBµV/m and V/m?
They describe the same electric field strength: dBµV/m is the decibel form referenced to 1µV/m, V/m is the linear form. 0dBµV/m=1 µV/m, and 120dBµV/m=1 V/m.
How do I convert dBm to watts?
P=1mW×10^(dBm/10). So 0dBm=1 mW and 30dBm=1W. Note the factor is 10, not 20, because dBm is a power unit.
Why 20·log for field strength but 10·log for power?
Power is proportional to the square of a field or voltage, so 10·log₁₀ of a power ratio equals 20·log₁₀ of the corresponding field ratio. Use 20·log for V, A, E, H, B; use 10·log for power and power density.