15 Db to DBM – Full Calculation Guide

The result of converting 15 dB to dBm is approximately 15 dBm.

Since 0 dB corresponds to 1 milliwatt (mW), adding 15 dB means the power level is 15 times higher in logarithmic scale. The conversion from dB to dBm involves treating the dB value as a ratio of power compared to 1 mW, so 15 dB equals 10 times the logarithm base 10 of the power in milliwatts, which results in 15 dBm.

Conversion Result

Conversion Formula

To convert from dB to dBm, the formula is: dBm = dB + 0, because dB already expresses a ratio of power level relative to 1 milliwatt (mW). When converting, if the dB value is directly a ratio of power, then an addition of 0 is done since 0 dB equals 1 mW. However, typically, if you have a power ratio, multiply by 10 to express it in dBm. For example, 15 dB corresponds to 10^(15/10) milliwatts, which is 31.62 mW, then expressed as 10 * log10(31.62) = 15 dBm.

Step-by-step math:

• Convert dB to milliwatts: 10^(15/10) = 10^1.5 = 31.62 mW
• Express as dBm: 10 * log10(31.62) = 15 dBm

Conversion Example

Let’s see how 20 dB converts to dBm:

• Calculate power in milliwatts: 10^(20/10) = 10^2 = 100 mW
• Express in dBm: 10 * log10(100) = 20 dBm

Similarly, for 5 dB:

• Power in mW: 10^(5/10) = 10^0.5 ≈ 3.16 mW
• dBm: 10 * log10(3.16) ≈ 5 dBm

And for -10 dB:

• Power in mW: 10^(-10/10) = 10^-1 = 0.1 mW
• dBm: 10 * log10(0.1) = -10 dBm

Conversion Chart

Below is a table showing dB values from -10.0 to 40.0 and their corresponding dBm values:

This chart helps to quickly see how dB values correspond to power in milliwatts expressed as dBm. Just match your value in the first column to find the equivalent in dBm in the second column.

Related Conversion Questions

• How do I convert -15 dB to dBm?
• What is the dBm equivalent of 25 dB?
• How can I convert 10 dB to milliwatts?
• What does 0 dB mean in terms of power in dBm?
• Is 20 dB equal to 20 dBm?
• How do I convert a 30 dB signal to dBm?
• What is the dBm value for a -5 dB signal?

Conversion Definitions

db: Decibels (dB) measure the ratio between two power levels on a logarithmic scale, indicating how much one value is amplified or attenuated compared to another, without inherent units, only ratios.

dbm: Decibel-milliwatts (dBm) express power levels relative to 1 milliwatt in a logarithmic scale, making it easier to compare and quantify signal strengths in communication and audio systems.

Conversion FAQs

How do I interpret 15 dB in terms of power levels?

15 dB indicates the power is roughly 31.62 times higher than 1 milliwatt, meaning the power level is about 31.62 milliwatts when converted to dBm, showing a significant increase in signal strength.

Can I directly add dB and dBm to get a new power level?

No, adding dB to dBm isn’t correct for calculating new power levels. Instead, you convert the dB value to milliwatts, then express the total power in dBm for accurate results, as they measure different things.

What is the difference between dB and dBm in practical use?

dB measures ratios between signals, useful for comparing power levels without fixed units, while dBm quantifies actual power levels relative to 1 milliwatt, providing absolute measurement which is useful in designing and analyzing communication systems.

How do I convert a power ratio in dB to a power in milliwatts?

To convert, use the formula: Power in mW = 10^(dB/10). For example, 15 dB: 10^(15/10) = 31.62 mW, giving the power in milliwatts.

Is 0 dB always equal to 1 mW?

Yes, 0 dB signifies that the power level is equal to the reference level, which in the case of dBm is 1 milliwatt, making it the baseline for comparisons.

Last Updated : 22 June, 2025

Sandeep Bhandari

Sandeep Bhandari holds a Bachelor of Engineering in Computers from Thapar University (2006). He has 20 years of experience in the technology field. He has a keen interest in various technical fields, including database systems, computer networks, and programming. You can read more about him on his bio page.