1. What is dBm?

dBm (decibels-milliwatts) is a unit of power measurement that expresses absolute power in decibels relative to 1 milliwatt. It's commonly used in radio, microwave, and fiber-optic communication networks.

2. Conversion Formula

The calculator uses the following formula:

Where:

• \( W \) — Power in watts
• 1000 — Conversion factor (1 watt = 1000 milliwatts)
• \(\log_{10}\) — Base-10 logarithm

Explanation: The formula converts watts to milliwatts (×1000) then calculates the logarithmic decibel value relative to 1 mW.

3. Practical Applications

Details: dBm is widely used in telecommunications to express signal strength, transmitter power, and amplifier gain. It provides a convenient way to work with very large and very small power levels.

4. Using the Calculator

Tips: Enter power in watts (W). The value must be positive. Common values range from nanowatts (1×10⁻⁹ W) to kilowatts (1×10³ W) in RF applications.

5. Frequently Asked Questions (FAQ)

Q1: What does 0 dBm represent?
A: 0 dBm equals exactly 1 milliwatt (0.001 W). Positive values are greater than 1 mW, negative values are less than 1 mW.

Q2: How does dBm compare to dB?
A: dB is a relative unit (ratio), while dBm is absolute (referenced to 1 mW). 3 dBm means 2 mW, while 3 dB means "twice the power" of some reference.

Q3: What's a typical WiFi signal strength?
A: Good signal is around -50 dBm, fair is -70 dBm, and below -80 dBm is usually too weak for reliable connections.

Q4: Why use logarithmic units?
A: Logarithmic scales conveniently represent very large ranges (e.g., 0.000000001 W to 100 W as -90 dBm to +50 dBm) and make multiplicative gains additive.

Q5: How to convert dBm back to watts?
A: Use \( W = 10^{(\text{dBm}/10)} / 1000 \). Our calculator may include this reverse calculation in future updates.