converting an extract recipe to AG...

What is the method for converting extract weight to grain weight?
I can see that the grain weight would be more, but don't know how much
Thanks to replies!

DME is 45 points of gravity per lb per gallon; LME is 37. Most base grains are in the 36-38 range, so if you get 75% efficiency you'll get ~28 points. So

lbs of grain = lbs of DME * 45/27 or
lbs of grain = lbs of LME * 37/27

You'll also need to adjust the hops for the higher utilizaton of a full boil.

Many of the software tools (ProMash, BeerSmith) will do this for you.

As long as you are doing a straight extract with specialty malts (ie no with no grains that require mashing or unmalted adjuncts) then you are only interested in converting the Pale or Base malt part of the recipe. Presumably the figures above are correct.

Once you work out the potential extract from the pale malt reduced to allow for the efficiency (usually 75%) you can then figure out how much lme/dme you require to produce the same value.

Instead of putting the specialty malts in the mash tun, just steep them instead.