P1dB to IP3 calculator
Estimate third-order intercept from the 1 dB compression point using a fixed dB offset. This is a rule of thumb, not a measurement — use a datasheet or measured IP3 when you have one.
Add gain to convert between input- and output-referred values.
9.6 dB is the theoretical spacing for an ideal third-order nonlinearity. 10 dB is the usual rule of thumb. Many power amplifiers run 12–15 dB or more.
Result
How this is estimated. IP3 is taken as P1dB plus a fixed offset Δ, on whichever reference plane (input or output) you entered. That offset is invariant to gain, so converting between input- and output-referred values only needs gain, not a re-measurement. Real devices deviate from a single fixed offset, sometimes by several dB, and the offset itself changes with bias, frequency, and how compression is defined — treat this as a starting estimate for budgeting, not a spec.