This is very easy...at least for me. It is mathematical and well, I like math... a lot... too much maybe...but I digress...
You have to start knowing how many pounds your machine holds. The standard sizes are 2 pounds, 1.5 pounds and one pound.
2 pound machine holds 4 cups of flours/grains.
1.5 holds 3 cups.
1 pound holds 2 cups.
(note this is just flours and grains... don't go and add in the sugars or dried milk!)
Add all the flours and grains in the recipe together. (In the recipe I gave last week the original recipe called for 10 cups of flour/grains... sure it make 2 or 3 loaves but would not fit in a bread machine!) Err on the side of too much flour (ex: if the recipe says something like "5 to 6 cups for kneading" go with the 6 in the math.)
For this math we are going to have you plug in numbers:
"P" is the percentage you need to multiply the WHOLE recipe by.
"B" is the number of cups you can fit in you bread machine.
"O" is the number of cups you got from the original recipe.
P = B/O
Plug in numbers and calculate.
Now take P and multiply it by each ingredient in the recipe. It is best if you don't have to round but if you do go out at least 2 decimal points before rounding.
The first time you make the "new" recipe check it out in the machine 5 minutes into mixing to see if it is too dry or is too wet. add one teaspoon of water of too dry and one teaspoon of grain if too wet and then wait another 5 minutes and check again. Continue until it looks good.