How many inches of penis can a woman take?

You cannot compare an object to a penis, for the most part. The penis even when erect is organic, and comforms in a natural and matching way to the inside of the vagina. So four inches of an object will not be comparative.

You're hitting your cervix with this object, but as the object is not organic, your cervix cannot naturally conform to the contours of the object. So it feels like hitting a wall, even as there is not really a wall there.

With insertion of the penis, and if the woman's moods are inviting, the woman's vagina could in nearly all cases take 7". If the woman has a naturally deeper cervix, then she might even be able to take up to 10".

Cheers.

I've heard up to 7 inches before it becomes painful. Some women though like and prefer it even bigger. I have a small one though, just 4 inches long. This small isn't very common though!

A woman can practice & take a lot. Even 12". There's empty space behind the vagina. The vagina also stretches. At first its resistant but with practice can take a lot.