How do you take ingredients from a brewer's website and make a recipe

The key to cloning is understanding how scaling and efficiency affects your particular home based brewery. As mash, kettle and fermentor sizes increase so does the effective outcome of each process on the end result. If your new to all this the best advice is to use an online recipe calculator, like Brewers Friend, keep good records, and remember it's as much about the process as it is about the recipe.

As the other answers say, you can go off the experience of others and use trial and error to dial in a recipe. I agree with them, but I also highly recommend Ray Daniel's "Designing Great Beers" for advice on how to go about formulating your own recipes. Since buying this book in 1998, I have only followed other people's recipes a few times.

Another thing you can do is go to this recipe builder and try entering all of the information you have, such as ingredients and batch size. It will calculate the information you requested (expected OG, FG, ABV, etc.). They also let you buy the recipe once you've calculated it, but the tool is still useful even if you don't buy the recipe. Some of the options may be a bit advanced, though.

Some breweries will give you their malt bill as a percentage. In this case, you're going to want to use software. You know the ABV (it's normally listed) and the percentage of each of the grains. Some software will let your select your batch size (ie: 5 gallons) and you can then enter the data you know (which grains and their percentage) and adjust the amounts until you get your desired ABV. A word of caution though... if you're making an IPA, the hops will be the key.

Another, more unconventional method would be to read (and reread) the book Designing Great Beers and try to emulate the beer you want to duplicate. Doing this, there are only 3 options... you succeed, you fail miserably (dump it out or give it to friends who wouldn't know the difference) or you fail spectacularly (this is when you actually have a beer that you like more than the beer you were trying to make).

Phantom Canyon used to give very detailed information for select brews like malt percentages, yeast strains and techniques (mash temps, adjuncts). That was not too difficult to translate into a very accurate recipe. But, I haven't seen one like that since they updated their website look a while back.

It's impossible to look at a beers ingredient list and derive an exact recipe from it. You have to go through a process of trial and error, using any information you can get from the manufacturer combined with experience or intuition.

However, the good news is that you probably won't have to do that yourself, because its highly likely someone else already has. Copying a commercial style is usually referred to as cloning, and for many beer styles you can simply google "commercial beer style + clone". Depending on how popular that beer style is, there might be a large number of recipes out there, or there might be a few dedicated people who have done all of the trial and error for you.

For example, a search for the Samuel Adams beer you linked to produces a few good leads and a fair amount of discussion. Sometimes its better to get discussions rather than straight recipes because it will help you to understand what is needed and why certain ingredients and processes are favoured over others.

Homebrewing forums usually have whole subforums dedicated to cloning, and the various homebrew software packages usually have ways of sharing recipes online to make it easy for others to find (BeerSmith for example.

Now, some recipes may use an all extract approach, some may use all-grain, and some may use a combination. So it's probably best to find a recipe that suits your experience and equipment. If you are just learning about homebrewing and have no idea how all-grain differs from all-extract, then you should read John Palmer's 'How to Brew' which is online. It covers everything a new brewer needs and then some.

I'd probably advise brewing from basic recipes before you get into cloning. Because once you have a fair amount of experience under your belt from that, you'll understand all the nitty gritty details like when to add which hops and how that will affect the beer etc.

Short answer: No.

There is no way to just look at a list of ingredients, with no quantities, and with great accuracy know how the beer is made, or what those quantities are. The best you can do is take educated guesses based on things like hoppyness, maltyness, sweetness, color, clarity and smell of the beer.

But, there is hope, as beer recipes are very scalable, once you know the ratios of malts, and hop schedules. For instance, doubling a 5 gallon recipe will give you a 10 gallon recipe, and quadrupling it will give you the 20 gallon recipe. Once you get into the hundreds of gallons at a time, I would think some of the quantities would need some tweaking, but not by much.

Also consider that even if you did know the recipe, you might have to alter it to fit your equipment and account for other factors in how you brew.