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EMC
Voltage

µV ↔ dBµV Calculator

Convert Microvolt (µV) and Decibel Microvolt (dBµV) in either direction with standard formulas.

µV
dBµV

Conversion Theory & Math Derivation

Mathematical Formulas:

µV to dBµV: dBµV = 20 * log10(µV)
dBµV to µV: µV = 10^(dBµV / 20)

Step-by-Step Derivation & Logic:

  1. dBµV represents voltage relative to 1 microvolt (µV).
  2. Linear microvolts to decibels: V(dBµV) = 20 · log10(V(µV)).
  3. Decibels back to linear microvolts: V(µV) = 10^(V(dBµV) / 20).

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Real-World Application

Legacy FCC text and some military / automotive annexes still print field or port limits in linear µV or µV/m, while modern EMI receivers, LISNs, and report templates speak almost exclusively in dBµV. This conversion is the daily bridge when refreshing old limit PDFs into digital dashboards or when an FAR/Cab calculation sheet still expects microvolts.

Worked Example

Example: FCC Part 15 Class B at 3 m for 30–88 MHz is historically 100 µV/m. Logarithmic form: 20 · log10(100) = 40 dBµV/m. That 40 dBµV/m line is what modern automated RE software draws.

Common Mistakes & Tips

0 µV is undefined in decibels (log of zero). A reading of 0 dBµV means exactly 1 µV—not 'no signal'. Receiver noise floors of −10 dBµV are simply sub-microvolt voltages, not instrument failure.

Frequently Asked Questions

Q: Can dBµV be negative?

A: Yes. Any voltage below 1 µV yields a negative dBµV (0.5 µV ≈ −6 dBµV).

Q: Is µV here the same as field strength µV/m?

A: Algebraically, the BI-to-dB conversion is identical. Physically, µV/m already includes the 'per meter' dimension—do not strip it when reporting.

Q: Why insist on 20·log10 instead of 10·log10?

A: Voltage and current ratios use 20; power ratios use 10. Using 10·log10 on microvolts incorrectly understates every change by a factor of two in draft-log terms.

Where is this used in EMC Standards?

These units are frequently used in official EMC test standards. Explore the limit lines below:

Calculator quality evidence

Purpose of this calculator

Use µV↔dBµV to move between a receiver or probe's linear microvolt reading and the logarithmic unit used on EMC voltage limit tables.

Formula and variables

For positive voltage V in µV: V(dBµV) = 20·log10(V); the inverse is V(µV) = 10^(V(dBµV)/20).

Physical assumptions and scope

The reference is exactly 1 µV and the logarithmic quantity is voltage, not field strength. The measured voltage convention must remain unchanged.

Valid input scope

µV input must be positive and finite; 1 µV is 0 dBµV. Zero or a negative voltage has no direct finite logarithmic magnitude without defining an absolute-value convention.

Independently checked test vectors

  1. 1 µV → 0 dBµV(forward)
  2. 0 dBµV → 1 µV(reverse)

Conversion-specific misuse to avoid

Do not append /m to dBµV unless you are intentionally converting the quantity to field strength; µV and µV/m are different physical quantities.

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