How do I convert between all-grain and extract recipes?

Question

If I have an all-grain recipe, and I want to convert it to an extract or partial-mash recipe, the easiest way is to replace the base malt with malt extract. Conversely, converting an extract recipe to all-grain involves using a base malt in place of the extract.

Is there a specific grain-to-extract ratio when doing such conversions? If it depends on the specific type of base malt, is there a table somewhere that shows the amount of potential fermentables that are available for different malts? Something that allows me to determine "X pounds of base malt == Y pounds of malt extract", and vice-versa.

Answer 1

Multiply your base malt weight by .75 do get the same (ish) amount in liquid extract.

For example - 10lbs. Pilsner malt = 7.5lbs Pilsner Liquid Malt Extract

For a Dry Malt Extract multiply by .6.

For example - 10lbs malt = 6lbs. Dry Malt Extract

Steep specialty grains as usual.

Answer 2

Matt's formula is what I've seen in several places. However, I'd add to that, that you should check the malt chart here (http://www.homebrewtalk.com/wiki/index.php/Malts_Chart) as well. In particular, note the "Mash Req." column, which indicates that a particular grain has to be mashed. If you're doing extract brewing, any ingredient that requires mashing will have to be replaced with extract.

Usually, that's just the base malt, but in some recipes, it can be more. Some of those "malt required" grains can be tricky to find. Make sure that any extract replacement is matched to the grain your replacing. For instance, if the recipe calls for Maris Otter, you want to get English Pale Malt Extract, not American if you want the taste to match.