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Electricity

dBm to Watts Conversion Calculator

Convert dBm to watts, watts to dBm, watts to dBW, dBm to milliwatts, and dBW with clear logarithmic power formulas and reference tables.

Interactive calculator

dBm to Watts Conversion Calculator

Convert dBm to watts, watts to dBm, dBm to milliwatts, dBW, and RMS voltage with impedance.

Negative dBm values are valid (power below 1 mW).

Logarithmic Power Scale

  • +10 dB → 10× power
  • +20 dB → 100× power
  • +30 dB → 1000× power
  • +3 dB ≈ 2× power

0 dBm = 1 mW · 30 dBm = 1 W

Common dBm Reference

dBmmWW
-300.0011 µW
-200.0110 µW
-100.1100 µW
011 mW
3≈2≈2 mW
101010 mW
20100100 mW
3010001 W
401000010 W
50100000100 W

Quick Guide

  • Choose a conversion mode (dBm↔W, dBm↔mW, dBW↔W, or Vrms).
  • Enter a value and click Calculate.
  • Use quick-fill chips for common dBm values.

Table of Contents

Key Takeaways

  • dBm is an absolute power unit referenced to 1 milliwatt (0 dBm = 1 mW).
  • 30 dBm equals 1 W; dBm to watts uses P(W) = 10^((dBm − 30) / 10).
  • Watts to dBm uses dBm = 10 log₁₀(P(W) / 0.001).
  • Watts to dBW uses dBW = 10 log₁₀(P(W)); 0 dBW = 1 W.
  • Every +10 dB means 10 times more power; +3 dB ≈ 2× power.
  • dB alone is a ratio; dBm and dBW are absolute because they have references.

What Is dBm?

dBm (decibel-milliwatt) expresses absolute RF or electrical power relative to 1 milliwatt. It compresses large power ranges into manageable numbers used in Wi-Fi, Bluetooth, radios, and telecom systems.

To relate RF frequency to wavelength, use the Frequency to Wavelength Calculator.

dBm to Watts Formula

P(W)=10((dBm−30)/10)P(W) = 10^((dBm − 30) / 10)

Subtract 30 because 30 dBm equals 1 watt. To convert watts to dBm: dBm = 10 log₁₀(P(W) / 0.001).

Watts to dBW

dBW=10log10(P(W))dBW = 10 log₁₀(P(W))

0 dBW = 1 W. Relationship: dBm = dBW + 30. Example: 10 W = 10 dBW = 40 dBm.

dB vs dBm vs dBW

dB is a ratio. dBm is referenced to 1 mW. dBW is referenced to 1 W. Relationship: dBm = dBW + 30. Typical Wi-Fi transmit power might be around +20 dBm (100 mW), while receiver sensitivity is often negative dBm.

How to Use

  1. Select conversion mode.
  2. Enter dBm, watts, milliwatts, or dBW.
  3. Click Calculate and review equivalents.

Examples

0 dBm

P(mW) = 10^(0/10) = 1 mW = 0.001 W.

30 dBm

P(W) = 10^((30−30)/10) = 1 W.

20 dBm

P(W) = 10^((20−30)/10) = 0.1 W = 100 mW.

1 W to dBW

dBW = 10 log₁₀(1) = 0 dBW.

Accuracy and Limitations

This calculator converts power units mathematically. It does not determine RF exposure, antenna gain, cable loss, or signal coverage. For safety-critical RF work, use professional verification.

FAQ

What is the formula to convert dBm to watts?›

P(W) = 10^((dBm − 30) / 10). For example, 30 dBm = 1 W and 0 dBm = 0.001 W = 1 mW.

What is 0 dBm in watts?›

0 dBm equals exactly 1 mW, or 0.001 W.

What is 30 dBm in watts?›

30 dBm equals 1 W.

How do you convert watts to dBm?›

dBm = 10 log₁₀(P(W) / 0.001). Power must be greater than zero.

How do you convert watts to dBW?›

dBW = 10 log₁₀(P(W)). 1 W = 0 dBW. Power must be greater than zero.

Is dBm the same as dB?›

No. dB is a ratio (relative). dBm is absolute power referenced to 1 mW.

Why can dBm be negative?›

Negative dBm means power below 1 mW. For example, −10 dBm = 0.1 mW.

Does +10 dBm mean 10 times more power?›

Yes. Every +10 dB corresponds to a 10× increase in power.

Can dBm tell me Wi-Fi range?›

No. dBm is a transmit or receive power level, not a direct measure of coverage or range.

Sources

  1. NIST: SI Units
  2. NIST SP 811: decibel and log quantities
Manish Kumar

Author & technical reviewer

Manish Kumar

PhysicsCalcs tools are reviewed with an educational focus: clear formulas, transparent assumptions, and practical context for students and science learners.

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