I have more than just a recipe for homemade brown sugar from scratch, check out more of my favorite recipes at the end of the page.
I have made my own brown sugar for years. You use white sugar, add molasses and mix well. I was running to the store for brown sugar until I discovered this easy substitute...
Light Brown Sugar: For each cup of white sugar add 2 tablespoons of molasses.
Dark Brown Sugar: For each cup of white sugar add 4 tablespoons of molasses.
Mix well with a fork. You may make a bunch and store in an airtight canister. This is half the cost of brown sugar you would buy at the grocery store.
If you store it, give it a good mix with a fork before measuring it out.