Use this easy tool to calculate the sensitivity (1w/1m) of a powered loudspeaker. Just enter your loudspeakers Max SPL and maximum Power. Then hit Calculate for your answer. This of course presumes that the manufacturers specification is accurate.
This is useful if you want to compare the efficiency of powered loudspeakers with passive loudspeakers. It can help you compare how much power different loudspeaker need to be as loud as each other. Remember a speaker with 3dB less sensitivity will need twice as much power to be as loud.
This calculator uses the formulas Published by Yamaha amongst others.