So you've nailed your favourite bread recipe and your sister/best friend/neighbour/Kevin from accounts now want a piece of the action. Can you just take the recipe and multiply it by 4 to make the extra? Nope.
The reason for this is that each ingredient has its own inherent characteristics and qualities which influence the ways in which it interacts with the others. Get the proportions wrong and your dough is very likely to misbehave.
The way to do it is to use baker's percentages. With this method all of the ingredients in a recipe are stated as percentages of the total flour weight. So, let's say your recipe has 600g of strong white flour and 400g of wholemeal, the combined flour weight is 1000g which is equal to 100%. The recipe has 700g of water, which is 70% of the total flour weight. 15g of salt is 15% and 2g of baker's yeast is 2%.
Once you have worked out the baker's percentages of your original recipe you can then easily scale the ingredients up or down as you like, or change up the flour blends to suit your tastes. Time to get out the BIG mixing bowl...