dBm to mW Converter: RF Power Calculator
Convert dBm to milliwatts instantly, or go the other way: milliwatts to dBm, plus watts and dBW in one live calculator. Built for WiFi planning, ham radio, and telecom work, with a full dBm to watts conversion table.
Live dBm to mW Calculator
Type in any field; the other three update live. Formula: P(mW) = 10dBm/10
The dBm to Milliwatts Formula
P(mW) = 10(dBm / 10)dBm (decibel-milliwatts) is a logarithmic unit referenced to 1 milliwatt. The reverse conversion is dBm = 10 x log10(P in mW). Because the scale is logarithmic, adding 10 dBm multiplies power by 10, and adding 3 dBm roughly doubles it. That is why radio engineers prefer dBm over watts when a link budget spans from picowatts at the receiver to kilowatts at the transmitter.
dBm to mW Conversion Table
| dBm | Milliwatts | Watts | dBW |
|---|---|---|---|
| -90 dBm | 1e-9 | 1e-12 | -120 |
| -80 dBm | 1e-8 | 1e-11 | -110 |
| -70 dBm | 1e-7 | 1e-10 | -100 |
| -60 dBm | 1e-6 | 1e-9 | -90 |
| -50 dBm | 1e-5 | 1e-8 | -80 |
| -40 dBm | 0.0001 | 1e-7 | -70 |
| -30 dBm | 0.001 | 1e-6 | -60 |
| -20 dBm | 0.01 | 1e-5 | -50 |
| -10 dBm | 0.1 | 0.0001 | -40 |
| 0 dBm | 1 | 0.001 | -30 |
| 3 dBm | 1.995262315 | 0.0019952623 | -27 |
| 10 dBm | 10 | 0.01 | -20 |
| 13 dBm | 19.9526231497 | 0.0199526231 | -17 |
| 20 dBm | 100 | 0.1 | -10 |
| 23 dBm | 199.5262314969 | 0.1995262315 | -7 |
| 30 dBm | 1000 | 1 | 0 |
| 33 dBm | 1995.2623149689 | 1.995262315 | 3 |
| 40 dBm | 10000 | 10 | 10 |
| 43 dBm | 19952.6231496888 | 19.9526231497 | 13 |
| 50 dBm | 100000 | 100 | 20 |
| 60 dBm | 1000000 | 1000 | 30 |
Anchor points are highlighted. Every value above is computed from P(mW) = 10^(dBm/10); 30 dBm = 1 W is the crossover between the mW and W worlds.
WiFi Signal Strength in dBm
Your phone's WiFi indicator hides the real number: received signal strength in dBm. Negative dBm is completely normal here because received power is far below 1 mW.
dBm vs dBW
dBm and dBW measure the same thing on the same logarithmic scale; they differ only in reference power. dBm references 1 milliwatt, dBW references 1 watt. Since 1 watt = 1000 mW = 30 dB above 1 mW:
dBW = dBm - 30So 30 dBm = 0 dBW = 1 W, 43 dBm = 13 dBW = 19.9526 W, and 60 dBm = 30 dBW = 1 kW. Use dBm for small-signal and receiver work, dBW for transmitter and broadcast power.
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Frequently Asked Questions
How do I convert dBm to mW?
Use the formula P(mW) = 10^(dBm/10). For example, 10 dBm becomes 10^(10/10) = 10^1 = 10 mW. Every 10 dBm step multiplies the power by 10, and every 3 dBm step roughly doubles it.
What is 0 dBm in mW?
0 dBm equals exactly 1 mW. dBm is defined relative to 1 milliwatt, so 0 dBm is the reference point: 10^(0/10) = 1 mW.
What is 30 dBm in watts?
30 dBm equals 1000 mW, which is exactly 1 watt. This is a key anchor: 0 dBm = 1 mW, 10 dBm = 10 mW, 20 dBm = 100 mW, and 30 dBm = 1000 mW = 1 W.
What is 20 dBm in mW?
20 dBm equals 100 mW. Using the formula: 10^(20/10) = 10^2 = 100 mW. This is the typical maximum transmit power of many WiFi routers.
How do I convert mW back to dBm?
Use the inverse formula dBm = 10 x log10(P in mW). For example, 50 mW becomes 10 x log10(50) = 16.9897 dBm, and 250 mW becomes 23.9794 dBm.
What is the difference between dBm and dBW?
Both are logarithmic power units; they differ only in reference. dBm references 1 milliwatt while dBW references 1 watt, so dBW = dBm - 30. For example, 30 dBm = 0 dBW = 1 W, and 43 dBm = 13 dBW = 19.9526 W.
Why are dBm values often negative?
Any power below 1 mW gives a negative dBm. For example, -30 dBm = 0.001 mW (1 microwatt) and -90 dBm = 0.000000001 mW (1 picowatt). Negative dBm is normal for received signals such as WiFi or cellular.
What is a good WiFi signal strength in dBm?
WiFi signal is measured in negative dBm: -30 dBm is excellent (near the router), -50 to -60 dBm is good, -70 dBm is weak, and below -80 dBm is nearly unusable. In milliwatts, -70 dBm is only 0.0000001 mW.
What does the 3 dB rule mean?
A 3 dB increase doubles the power and a 3 dB decrease halves it. For example, 3 dBm = 1.9953 mW (about double 0 dBm = 1 mW), and going from 20 dBm (100 mW) to 23 dBm gives about 200 mW.
How many watts is 50 dBm?
50 dBm equals 100,000 mW, which is 100 watts. The chain is 40 dBm = 10 W, 50 dBm = 100 W, and 60 dBm = 1000 W = 1 kW.
What is 5 watts in dBm?
5 watts equals 36.9897 dBm. Convert watts to milliwatts first (5 W = 5000 mW), then apply dBm = 10 x log10(5000) = 36.9897 dBm.
Why do engineers use dBm instead of watts?
Radio power spans enormous ranges, from picowatts at a receiver to kilowatts at a transmitter. The logarithmic dBm scale compresses this into manageable numbers: -90 dBm (1 pW) to 60 dBm (1 kW) covers 15 orders of magnitude in just 150 units.
Is a higher dBm value always better?
For received signal strength, yes: -50 dBm is much stronger than -80 dBm. For transmit power, higher dBm means more output power but also more energy use and potential interference, so regulations cap WiFi at 20 dBm (100 mW) in many regions.
Can dBm be converted to voltage?
Yes, if you know the impedance. Power in watts = V^2 / R, so at 50 ohms, 0 dBm (1 mW) equals about 0.2236 V RMS. Our voltage converter tool handles dBmV and dBuV conversions with 50 and 75 ohm references.
Free tool by NRTechStudio