The dbm Calculator & Reference table for 50 Ohms
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The dbm Calculator & Reference table for 50 Ohms

What is dBm?

A logarithmic ratio with a reference power of P0 = 1.000 milliwatt = 0 dBm.

dBm is defined as a power ratio in decibels (dB) referenced to one milliwatt (mW), and the “m” in dBm stands for milliwatt.

With a known impedance value, you can convert voltage V to level dBm (power) and vice versa.

Reference voltage at 600 Ω — 1 mW (0 dBm)

Reference voltage at 600 ohms for 1 mW

Reference voltage at 50 Ω — 1 mW (0 dBm)

Reference voltage at 50 ohms for 1 mW

dBm / Voltage / Impedance Calculator

Enter any two values – the third will be calculated.
Voltage V, Level L, Impedance Z
Voltage V V RMS
Power Level L dBm re 1 mW
Impedance Z Ω

Table based on 50 Ohms

μV dBm Watts mV dBm Watts V dBm Watts
0.7-11010fW1.1-461.1+140.025
0.8-109S31.2-451.2+150.032
0.9-1081.4-441.4+160.04
1-1071.5-43S9+301.5+170.05
1.1-1061.7-421.7+180.063
1.2-1051.9-411.9+19 0.08
1.4-1042.2-40100nW2.2+200.1
1.5-103S42.5-392.5+210.13
1.7-1022.8-382.8+22 0.16
1.9-1013.1-373.1+230.2
2.2-100100fW3.5-363.5+240.25
2.5-993.9-353.9+25 0.3
2.8-984.4-344.4+260.4
3.1-97S55.0-33S9+405.0+270.5
3.5-965.6-325.6+28 0.63
3.9-956.3-316.3+290.8
4.4-947.0-301μW7.0+301.0
5-93S9 VHF/UHF7.9-297.9+311.2
5.6-928.9-288.9+321.5
6.3-91S69.9-279.9+33 2.0
7-9011-2611.2+342.5
7.9-8913-2512.5+353.1
8.9-8814-2414.1+363.9
9.9-8715-2315.8+375.0
11-8617-2217.7+38 6.3
13-85S719-2119.9+397.9
14-8422-2010μW22.3+4010
16-8325-19
18-8228-18
20-8132-17
22-8035-16
25-79S840-15
28-7845-14
32-7750-13
35-7656-12
40-7563-11
45-7471-10100μW
50-73S979-9
56-7289-8
63-71100-7
71-70100pW112-6
79-69126-5
89-68141-4
100-67158-3
112-66178-2
126-65199-1
141-6422401mW
158-63S9+10251+1
177-62282+2
200-61316+3
223-601nW354+4
251-59398+5
282-58446+6
316-57501+7
354-56562+8
398-55630+9
446-54707+1010mW
500-53S9+20793+11
561-52890+12
630-511000+13
707-5010nW
793-49
890-48
1000-47S9+26

Understanding the dB Ratio:

This tutorial video link above gives the basics of the typical amplitude units used on a spectrum analyzer. It provides a basic description of the electronic definition of the decibel (dB), some of the properties of the dB, and why it is used. The dB is a relative measurement. These relative measurements can be expressed as absolute measurements when a known reference is used or implied. This is where the terms dBm, dBu, dBmv, etc., come from. Finally, the term dBc is described. Each of the descriptions is followed with practical examples and demonstrations on an oscilloscope and spectrum analyzer.

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