EMC Cheat Sheet (one printable page)

The values looked up most often on the test floor, on a single A4 page. The print button below gives a clean sheet without the menu and links.

In the print preview, keep the scale at 100 % and margins at "default" to fit one A4 page.

dB ↔ ratio

dB	Power	Voltage / field
1 dB	×1.26	×1.12
2 dB	×1.58	×1.26
3 dB	×2	×1.41
6 dB	×3.98	×2
10 dB	×10	×3.16
20 dB	×100	×10
30 dB	×1000	×31.6
40 dB	×10000	×100
60 dB	×10⁶	×1000
80 dB	×10⁸	×10000
100 dB	×10¹⁰	×10⁵

Anchors worth memorizing

Level	Value
0 dBm	1 mW
30 dBm	1 W
60 dBm	1 kW
0 dBµV	1 µV
60 dBµV	1 mV
120 dBµV	1 V
0 dBµV/m	1 µV/m
120 dBµV/m	1 V/m
140 dBµV/m	10 V/m

Formulas used most often

E [dBµV/m] = reading + antenna factor + cable − preamp
Margin [dB] = limit − measured, with uncertainty = margin − U
Distance scaling [dB] = 20·log₁₀(d₁ / d₂) (far field)
λ [m] = 300 / f [MHz]
At 50 Ω: dBµV = dBm + 107
Power uses 10·log₁₀; voltage, current and field use 20·log₁₀
Combined uncertainty: u = √(u₁² + u₂² + …), U = 2u (95 %)

Measurement bandwidth (CISPR 16-1-1)

Frequency	RBW
9 – 150 kHz	200 Hz
0.15 – 30 MHz	9 kHz
30 MHz – 1 GHz	120 kHz
Above 1 GHz	1 MHz

SI prefixes

Symbol	Factor
T	10¹²
G	10⁹
M	10⁶
k	10³
m	10⁻³
µ	10⁻⁶
n	10⁻⁹
p	10⁻¹²

Checks on the test floor

A broad lift in conducted emissions points to common mode first: clamp a current probe on each cable.
A single frequency spiking means a clock harmonic meeting a resonance (cable length or enclosure).
Use the standard’s own values for the 3 m and 10 m limits; do not scale them with the distance formula.
Subtract preamp gain, add cable loss. Getting the sign backwards is the most common error.
A margin smaller than U is an overlap, not a pass or a fail. Follow your laboratory’s decision rule.

The derivation and worked examples for each value are on the calculator pages. · emctoolbox.com

All conversion tables

Results and summaries are for reference. For certification and test reports use the latest official standard text and calibrated instrument data. Last updated: 2026-10-10