Brew Kettle size for full boils

I currently brew 5 gallon extract batches and would like to venture into all grain. I inherited (free is good!) a 7 gal stainless brew kettle. Would this work for full boil 5 gallon batches or would I need a 10 gal for a full boil on a 5 gal batch?

Any advice would be greatly appreciated.

Thanks!

7 is gonna be pushing it 8 is ok but you have to watching like a hawk. 10 is the best if you want to not really worry a about a boil over.

I have a 7.5 gal pot which I fill to about an inch from the top, the break at the beginning of the boil and everytime I add hops I have to have one hand on the gas and another with a spray bottle on foam control. I end up with about 5-5.5 gal after boil. 7 would be fine if you don't mind only getting 4.5-5 gallons out of it. Which for a free pot isn't that bad.

Thanks for the input two_one_seven and JollyIsTheRoger.

I started with extract batches in a 4 gallon pot.

When I went to AG, I thought a 7.5 gallon pot would be good for 5 gallon batches, but found that it was just a bit too small.

I then bought a 11 gallon (44 qt) Bayou Classic SS pot. This is the JUST RIGHT size for full boil extract AND all grain BIAB batches. I can do up to about 7 gallon batches if I want to. An 11 gallon pot is about $20 more than a 7.5 gallon....go ahead and spring for a 10-11 gallon kettle and you won't regret it!!

Thanks TropherM. I ended up purchasing a 10.5 SS kettle on eBay brand new for $87. Brew day this Saturday can't come fast enough!

I started 5g AG batches with a 7.5g kettle.
I never had a boil over, but I had to keep a very close eye on it.
Then when the first kettle died, I got myself a 10g kettle.
Since then, I've had several boil overs.
One day I may learn that I have to keep an eye on the brew as it is coming up to the boil in a 10g kettle, but I wouldn't like to bet on it.

-a.