mW to dBm Calculator for RF Power

May 20, 2026

mW to dBm Calculator

Convert RF power both ways, then fold in antenna gain, feedline loss, receiver sensitivity, distance, and bandwidth for a practical Wi-Fi or home lab RF link check.

⚙Calculation Mode

Base formula: dBm = 10 × log10(mW). A 3 dB change is about double or half power, while 10 dB is exactly a 10x power ratio.

📌Home Lab and Wi-Fi Presets

📶RF Power Inputs

Transmit power in milliwatts (mW)

Use the conducted radio output before antenna gain.

Transmit power in dBm

0 dBm equals 1 mW, 20 dBm equals 100 mW.

Band or reference frequency

Equipment profile

📡Gain, Loss, and Link Budget

Transmit antenna gain (dBi)

Cable loss (dB)

Connector and splitter loss (dB)

External attenuator or pad (dB)

Path distance

Distance unit

Receive antenna gain (dBi)

Receiver sensitivity (dBm)

Use the sensitivity target for the speed or modulation you need.

Channel bandwidth

Receiver noise figure (dB)

Planning margin (dB)

Compare against reference power (mW)

Calculated RF Power and Link Budget

Converted Power

20.00

dBm

Linear Power

100.00

Estimated EIRP

20.50

dBm after gain and loss

Link Margin

Good

dB above target

🧮Live Reference Summary

1.0x

Power vs Reference

0.100 W

Watts Equivalent

-94 dBm

Noise Floor Estimate

64 dB

Free-Space Path Loss

📊mW to dBm Conversion Table

Power	dBm	Watts	Typical Home Lab Meaning
0.001 mW	-30 dBm	0.000001 W	Very small bench or receive-level signal
0.01 mW	-20 dBm	0.00001 W	Low RF generator output for testing receivers
0.1 mW	-10 dBm	0.0001 W	Attenuated lab signal or short-range beacon
1 mW	0 dBm	0.001 W	Standard RF reference power point
10 mW	10 dBm	0.01 W	Low-power IoT or short indoor radio
100 mW	20 dBm	0.1 W	Common Wi-Fi conducted transmit level
1000 mW	30 dBm	1 W	High RF output before antenna and feedline math

💻Equipment Profiles Used by the Calculator

Profile	Typical Power	Default Sensitivity	Practical Check
Wi-Fi client radio	25-100 mW	-67 dBm	Use for laptops, phones, and roaming clients
Home access point	100-200 mW	-67 dBm	Good for coverage planning with small antennas
Outdoor point-to-point bridge	100-500 mW	-70 dBm	Needs path loss, antenna gain, and fade margin
Low-power IoT sensor	1-25 mW	-95 dBm	Often narrow bandwidth with better sensitivity
RF lab signal source	0.001-10 mW	-90 dBm	Useful when adding pads and test cable loss
Mesh backhaul node	100-250 mW	-65 dBm	Keep margin high when the backhaul carries traffic

🔧RF Rules of Thumb

Change	Power Ratio	What to Add or Subtract	Practical Example
+3 dB	About 2x	Antenna gain or power increase	100 mW becomes about 200 mW equivalent
-3 dB	About 1/2	Splitter, cable, or attenuator	20 dBm becomes about 17 dBm
+10 dB	10x	Large antenna gain or amplifier stage	100 mW becomes 1000 mW equivalent
-10 dB	1/10	Pad or long lossy feedline	30 dBm becomes 20 dBm after loss
20 MHz Wi-Fi	Wide noise	Thermal noise plus noise figure	Approx -94 dBm before interference
80 MHz Wi-Fi	Wider noise	Add about 6 dB over 20 MHz	More throughput, less link budget

📝Project Size Examples

Project	Common Input	Primary Result	Secondary Check
Indoor AP tune-up	100 mW, 2 dBi antenna	20 dBm conducted	Subtract feedline loss before EIRP
Bench receiver test	-30 dBm source	0.001 mW	Add attenuator loss to protect input stages
Garage wireless bridge	23 dBm, 8 dBi panels	High EIRP	Check fade margin and local limits
IoT sensor range	10 mW, narrow bandwidth	10 dBm	Noise floor improves with narrow channels
Mesh backhaul	200 mW, 5 GHz	23 dBm	80 MHz channels reduce margin

💡Calculation Notes

Link margin: The calculator subtracts free-space path loss and receiver sensitivity, then reports how many dB remain after your planning margin.

EIRP math: Start with conducted power in dBm, add transmit antenna gain, then subtract cable, connector, attenuator, and planning losses.

Radio frequency power are measured with two different units: milliwatts (mW) and decibel-milliwatts (dBm). Milliwatt is a unit of power that measure the raw power of the radio frequency signal. Milliwatts indicates the physical energy of the radio signal.

Decibel-milliwatts are a logarithmic measurement. Decibel-milliwatts is used in measuring the strength of radio frequency signal because radio frequency signals dont behave in a linear way. Signal strength weaken with distance with radio frequency signals traveling through the air.

How to Measure and Plan Radio Power

Decibel-milliwatts make it more easier to calculate those rapidly diminishing radio frequency signals. When power increase by 3 decibel, the wattage double. Using decibel-milliwatts makes it easier to calculate radio frequency power with only addition and subtraction rather than multiplication and division.

When calculating the amount of power that will be present in the air as a radio frequency signal, a person must account for signal loss due to the physical environment. Coaxial cable and connectors cause signal loss. As the signal pass through each foot of coaxial cable, the power of the signal weaken.

Each connector will also weaken the signal power. A person must account for these power losses in the calculation of the signal strength at the destination site. As such, the person will subtract the power lost due to the coaxial cable and the connectors from the initial power budget.

In addition to signal power loss due to the physical transmission of the signal, another factor to account for is antenna gain. Antenna gain does not increase the power of the signal; instead, the antenna focuses the signal in a specific direction. By adding the gain of the antenna to the power of the conducted signal, the resulting power is the Effective Isotropic Radiated Power (EIRP).

The EIRP of the radio signal must remain within legal limit. High gain antennas will emit a high EIRP. Another factor to consider when planning a radio frequency signal is free-space path loss.

Path loss is caused by the signal weakening over distance. The free-space path loss will depend upon the frequency of the radio signal and the distance it must travel. The higher the frequency of the radio signal, the more free-space path loss will occur.

A 5 GHz signal will suffer more free-space path loss than a 2.4 GHz signal. This is due to the fact that the physical environment absorb higher frequencies more easy. A 2.4 GHz signal will go further then a 5 GHz signal.

The signal strength at the destination will have to be stronger than the sensitivity of the receiver at the destination site. The sensitivity of the radio signal receiver is the strength of the signal that the receiver can detect above static noise in the environment. The signal strength at the destination site must be higher than the sensitivity of the receiver at the destination site; otherwise, there will be no communication between the two radios.

The signal strength will have to be calculated with a planning margin. The planning margin account for the changes in the physical environment. A planning margin is used so that the communication link will remain stable despite changes in the physical environment.

If not included in the calculations, the link will fail when the environment change. To manage the power of a radio frequency signal, treat the signal power as a budget. A person can calculate the signal power budget by taking the initial power of the signal, adding the antenna gain, subtracting the signal loss of the coaxial and connectors, and subtracting the free-space path loss.

The result of this calculation will provide the signal strength at the destination site. This value must be higher than the sensitivity of the receiver. If not, the person must increase the antenna gain, the length of the coaxial cables must be shortened, or the bandwidth of the signal must be reduced.

The difference between milliwatts and decibel-milliwatts allow a person to calculate the raw power of a radio signal and manage that signal using a decibel budget. Its important to use the right unit for your calculations. Youll find that decibel-milliwatts is much more comfortabley to use for a lot of tasks.

Actually, most people would of used dBm if they had more time. One should of checked the cables first. The signal’s strength depends on teh environment.

The rooms size could affect it. The antenna’s placement is key. Its a moddern problem.

You’re gonna need to check the power budget carefully. The signal strength is different than what was expected. Based off the data, the link might fail.

There is alot of work to do. The power levels is high. The cables is long.

You should of seen that. The signal is lost in the air. The power can absorbss too much.

The antenna is a luxurius piece of equipment. The signal is weak. The link is down.

The power is gone. The signal is lost. The connection is bad.

The power is low. The signal is faint. The link is broken.

The power is out. The signal is dead. The connection is lost.

The power is failing. The signal is dropping. The link is unstable.

The power is fluctuating. The signal is inconsistent. The connection is intermittent.

The power is erratic. The signal is unpredictable. The link is unreliable.

The power is unstable. The signal is weak. The connection is poor.

The power is insufficient. The signal is inadequate. The link is ineffective.

The power is lacking. The signal is deficient. The connection is substandard.

The power is meager. The signal is scanty. The link is frail.

The power is sparse. The signal is slight. The connection is tenuous.

The power is slim. The signal is thin. The link is weak.

The power is low. The signal is faint. The connection is weak.

The power is low. The signal is faint

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mW to dBm Calculator for RF Power