Too much carbonation

So, don't laugh at me, this is my second batch of brew. I open the bottles after carbonation and they instantly overflow. Did I use too much priming sugar? If so how do I know how much to use? The first batch I did had detailed instructions (kit I got for Christmas). The second batch didn't have many instructions I just used a recipe and followed what I did for the first batch. Any help would be appreciated

Overcarbonation has one of three possible causes.

1.  Too much bottling sugar.  I tend to use the low end of the carbonation range for thee style, so that I don't use too much sugar.
2.  Bottling too early, before fermentation is complete.  Patience solves this one.
3.  Contamination.  Look for a ring inside the bottle at the fill level.  There isn't always a ring in a contaminated bottle, but it is a solid indicator that you have contamination when you do have a ring.

Ok. I bet I used too much sugar. It's a stout and I used the same amount of sugar for the blond I made in the first batch. I let it ferment for 3 weeks and didn't see any type of contamination ring around the bottle. **another nub question** how do I determine how much priming sugar to use?

Beersmith has a carbonation in the tools tab.

There is also a second one on the recipe design page. It is on the fermentation tab.

Thank you!! I'll check it out.