yeast attenuation and alcohol

[trickrick]

I am trying to put together a Porter and want to kick it up a bit. This will be a 5 gallon batch.

I am using a 4lbs can of a porter extract and 4lbs of light DME, grains and hop additions.

8lbs of fermentable sugars seems high but I have read recepies with much higher amounts

Will White labs WLP005 British ale attenuation of 67 to 74 be enough to convert the fermentables to a higher alcohol %?

Is there a rule of thumb for attenuation of yeast and the amount of fermentable sugars to get a higher alcohol level?

ANY in put is appreciated, Thanks Rick

[Fast_Eddy]

Off the top of my head you're looking at about a 6.6% abv beer - WLP005 should be fine with maybe a little residual sweetness.

[Caffinehog]

Higher attenuation means a higer percentage of the sugars are consumed by the yeast. There are yeasts out there that attenuate better, but they'll really, at most, result in about a 0.5% increase in alcohol. This will also result in a dryer beer, less true to style.
I wouldn't add all that much more malt, and if you do, you'll have to adjust the hops. I'd try this one first, and if you still want more kick, brew the next one with more. As previously mentioned, this one should have plenty of kick.

Edit: Your beer should result in 5.6%-6.15% alcohol with that yeast and amount of malt. The most you could expect with a highly attenuative ale yeast would be 6.65% You could exceed this value with the current yeast simply by adding about 2/3 lbs. of malt extract. If you do so, up the hops about 10%.