How long should a tang be?

[Hesparus]

I'm in the process of forging a blade that will be my first hidden tang knife, and I'm not sure how long to make the tang. It will not be held on with a nut, but it will be pinned and epoxied. The blade looks like it'll turn out to be around 7".
Thanks,
Chris

 

[SBuzek]

As long as you can make it,with a 7" blade about 4" of tang.
Stan