thank you so much for your time. I am doing an application in which I know the rms value of the voltage I am delivering at the output ( I mean the digital rms value). Then if i know the user has a headphone with a sensitivity of X dB/V, if we get 1 Volt of rms value with the voltmeter I know...

any help please?

I don't know how u got that formula:   if dB/mW=10 log P/p=10 log(( V^2/R)/p)  since P=V^2/R and p=0.001Watts   then dB/mW=10 log(( V^2/R)/p)=10 log V^2 +10 log(1/(R*p))=20 log V +10 log(1/R*p)   I  know  i am wrong but i don't know where i mistook. can u help me?   thanks