The table below shows the ratio and voltage equivalent to a given level in dBu from +40 dBu to -40 dBu. dBu is a logarithmic voltage notation relative to 0.7746 Volts but not related to any impedance. dBm (the traditional unit 50 years ago) is relative to 1 mW into 600 ohms and is numerically equal to dBu. dBV (rarely used) is relative to 1.0 Volts and like dBu, is not related to any impedance.
| dBu | Ratio | Voltage | dBu | Ratio | Voltage | |
| 0 | 1.00 | 0.7746 | 0 | 1.000 | 0.7746 | |
| 1 | 1.12 | 0.8691 | -1 | 0.891 | 0.6904 | |
| 2 | 1.26 | 0.9752 | -2 | 0.794 | 0.6153 | |
| 3 | 1.41 | 1.0941 | -3 | 0.708 | 0.5484 | |
| 4 | 1.58 | 1.2277 | -4 | 0.631 | 0.4887 | |
| 5 | 1.78 | 1.3774 | -5 | 0.562 | 0.4356 | |
| 6 | 2.00 | 1.5455 | -6 | 0.500 | 0.3882 | |
| 7 | 2.24 | 1.7341 | -7 | 0.447 | 0.3460 | |
| 8 | 2.51 | 1.9457 | -8 | 0.398 | 0.3084 | |
| 9 | 2.82 | 2.1831 | -9 | 0.355 | 0.2748 | |
| 10 | 3.16 | 2.4495 | -10 | 0.316 | 0.2449 | |
| 11 | 3.55 | 2.7484 | -11 | 0.282 | 0.2183 | |
| 12 | 3.98 | 3.0837 | -12 | 0.251 | 0.1946 | |
| 13 | 4.47 | 3.4600 | -13 | 0.224 | 0.1734 | |
| 14 | 5.01 | 3.8822 | -14 | 0.200 | 0.1546 | |
| 15 | 5.62 | 4.3559 | -15 | 0.178 | 0.1377 | |
| 16 | 6.31 | 4.8874 | -16 | 0.159 | 0.1228 | |
| 17 | 7.08 | 5.4837 | -17 | 0.141 | 0.1094 | |
| 18 | 7.94 | 6.1528 | -18 | 0.126 | 0.0975 | |
| 19 | 8.91 | 6.9036 | -19 | 0.112 | 0.0869 | |
| 20 | 10.00 | 7.7460 | -20 | 0.100 | 0.0775 | |
| 21 | 11.22 | 8.6911 | -21 | 0.089 | 0.0690 | |
| 22 | 12.59 | 9.7516 | -22 | 0.079 | 0.0615 | |
| 23 | 14.13 | 10.9415 | -23 | 0.071 | 0.0548 | |
| 24 | 15.85 | 12.2765 | -24 | 0.063 | 0.0489 | |
| 25 | 17.78 | 13.7745 | -25 | 0.056 | 0.0436 | |
| 26 | 19.95 | 15.4552 | -26 | 0.050 | 0.0388 | |
| 27 | 22.39 | 17.3411 | -27 | 0.045 | 0.0346 | |
| 28 | 25.12 | 19.4570 | -28 | 0.040 | 0.0308 | |
| 29 | 28.18 | 21.8311 | -29 | 0.036 | 0.0275 | |
| 30 | 31.62 | 24.4949 | -30 | 0.032 | 0.0245 | |
| 31 | 35.48 | 27.4837 | -31 | 0.028 | 0.0218 | |
| 32 | 39.81 | 30.8372 | -32 | 0.025 | 0.0195 | |
| 33 | 44.67 | 34.6000 | -33 | 0.022 | 0.0173 | |
| 34 | 50.12 | 38.8218 | -34 | 0.020 | 0.0155 | |
| 35 | 56.23 | 43.5588 | -35 | 0.018 | 0.0138 | |
| 36 | 63.10 | 48.8737 | -36 | 0.016 | 0.0123 | |
| 37 | 70.79 | 54.8372 | -37 | 0.014 | 0.0109 | |
| 38 | 79.43 | 61.5284 | -38 | 0.013 | 0.0098 | |
| 39 | 89.12 | 69.0360 | -39 | 0.011 | 0.0087 | |
| 40 | 100.00 | 77.4597 | -40 | 0.010 | 0.0077 |
OTHER USEFUL INFORMATION:
To convert max level at 50 Hz to 20 Hz subtract 7.96 dB
To convert an rms voltage to a peak voltage multiply by 1.414
To convert an rms voltage to a p-p voltage multiply by 2.828
To convert a dB value to a ratio in Excel: Ratio =POWER(10,dB/20)
To convert a ratio to a dB value in Excel: dB =20*LOG(ratio)
