TOOL 01 / RF FOUNDATIONS
RF Power & Units
From watts to decibels. Every reference, every equation, in view.
Power converter
ABSOLUTE LEVELDecimal or scientific notation, e.g. 1e-6. Changing the unit reinterprets the entered value.
Results update as you type.
Average power dissipated in a pure resistance. This is the loaded RMS voltage.
Power ratio
RELATIVEConvert a change in power between dB and a linear multiplier, P₂ / P₁.
Positive dB = increase; negative dB = decrease. P₁ must be greater than zero.
dB
3 dB is close to doubling. Exactly ×2 is 3.0103… dB.
r = 10ΔdB / 10ΔdB = 10 log₁₀(r)Precision applies throughout: linear values use significant figures; dB uses 3 decimal places. Display rounding does not change the calculation.
AT A GLANCE
Quick references
Absolute power
50 Ω load| dBm | dBW | Power | V RMS |
|---|
The voltage column follows your load setting above.
Power change
P₂ / P₁| Change (dB) | Power multiplier |
|---|
±3 dB and ±6 dB are approximate doubling / quadrupling rules.
Equations & assumptions
SHOW THE WORKAbsolute power
1 W = 10³ mW = 10⁶ µW = 10⁹ nW
LdBW = 10 log₁₀(P / 1 W)
LdBm = 10 log₁₀(P / 1 mW) = LdBW + 30
P [W] = 10LdBW / 10 = 10(LdBm − 30) / 10
dBm and dBW are absolute levels with different references. dB alone expresses a ratio. Zero linear power has no finite logarithm; it is shown as −∞ dBm / dBW.
Resistive load & ratios
P = VRMS² / R → VRMS = √(P · R)
ΔdB = 10 log₁₀(P₂ / P₁)
Power is the average real power delivered to the stated, purely resistive load. No source impedance, mismatch, cable loss or reactive impedance is modelled. RMS does not require a sine wave under this assumption; peak and peak-to-peak voltage depend on waveform and are not calculated.
The 20 log₁₀ voltage-ratio rule corresponds to power ratios only when both resistances are equal. Here all ratio calculations use powers and the factor 10.
Supported ranges, rounding & verification
Power: zero, or 1e-30 to 1e30 W; equivalently −300 to +300 dBW / −270 to +330 dBm. Enter zero in a linear unit. All numeric inputs must be finite.
Load: 1e-6 to 1e9 Ω. Ratio: zero, or 1e-30 to 1e30 (−300 to +300 dB). A zero ratio means P₂ = 0 with P₁ > 0 and is shown as −∞ dB; 0 / 0 is undefined.
Input: dot decimals and scientific notation; no separators or unit suffixes. A Unicode minus sign is accepted. These numerical limits keep all supported calculations comfortably within floating-point range; they are not component ratings.
Display: choose 3, 6 or 9 significant figures for linear results; dB values use 1, 3 or 6 decimal places respectively. Scientific notation is used below 0.001 or from 1,000,000. Zero displays as 0. Trailing zeroes indicate display precision, not measurement accuracy.
Calculation: JavaScript double precision, with rounding only for display. Calculation checks cover published anchors, invalid inputs, zero, boundary values and reference tables, with separate high-precision numerical comparisons. Numerical checks do not establish measurement accuracy or suitability for a particular installation.
Equation references: ITU-T B.12, Annex A (historical; withdrawn) · Analog Devices, Measurement and Control of RF Power (Part I). These external references need internet access; calculations run in your browser after the page loads.