Demerara sugar and brown sugar can be classified as brown sugars since neither is perfectly white and both contain molasses. Aside from those common traits, you will find they are quite different products. You will want to compare their differences and similarities when choosing which one to use. We take a look at their properties in the SPICEography Showdown below.
How does demerara sugar differ from brown sugar?
Demerara sugar and granulated sugar are made using different processes. Demerara sugar comes from the juice extracted when the sugar cane is first pressed. It is considered a raw sugar because it undergoes very little processing. The sugarcane juice is evaporated until it crystallizes with some of its natural molasses intact.
Demerara Sugar 
Dark Brown Sugar 
Light Brown Sugar
Brown sugar is made from refined white sugar colored and flavored with molasses. The refinement process for the white sugar involves extensive processing stages including melting and carbonation along with filtration.
One of the key differences between demerara sugar and brown sugar has to do with crystal sizes. The size of the sugar crystals impacts appearance and mouthfeel. Demerara sugar has larger crystals than brown sugar. The crystals aren’t dramatically larger but the size difference can impact both the way they look and the crunch they provide when used as a topping for baked goods.
Flavor is another key area where demerara sugar and brown sugar differ. The darker a sugar is, the greater its molasses content will be. More molasses means that the sugar has a stronger molasses flavor. Demerara sugar is a darker sugar than some types of brown sugar. In addition to having more molasses flavor, demerara sugar has undergone less processing which may give it a purer flavor profile.
If your recipe calls for one, can you use the other?
All culinary sugars have a similar enough level of sweetness that you can use any granulated sugar in place of another and expect roughly the same degree of sweetening.
That said, the flavors of demerara sugar and brown sugar are not exactly alike and the appearances differ as well. You can use demerara sugar as a table sugar for sweetening oatmeal or coffee in much the same way that you might use brown sugar. However, the large grain size may make it a difficult substitute in some baked goods where it may not dissolve quickly and thus affect the texture of the finished product.
Brown sugar can work as a substitute for demerara sugar when it is used as a table sweetener. It will provide some of the same flavors since it also contains molasses. It may not be as effective as a finishing sugar due to its small grains.
When should you use demerara sugar and when should you use brown sugar?
Because of its large crystal-size, demerara sugar makes an attractive topping on baked goods. Like finishing salts, the size of the crystals means that it will not dissolve as quickly as finer sugars. The large crystals also give the baked goods a pleasant crunch. It makes a good topping for everything from muffins to scones.
Use brown sugar in dishes where you want its toffee caramel notes and brown color. It is great when you need a richly flavored sweetener at the table for oatmeal or coffee. You can also use brown sugar in a variety of baked goods like apple pies and brown sugar cookies.