Is your Flaccid Stretched Length equal to your Erect Length?

Is it true that when you stretch you gain length thats why your gaining length gains and not due jelqing? Because my flaccid stretched length is equally growing next to my erect length. Thats why im sceptical about jelqing being good for length gains?

And Im having a hard time measuring my flaccid stretched penis with bone pressed any tips?

Thanks in advance!