Every sofa is different but we've managed to classify them down to several standard shapes and size. To get a broad understanding, check this article out: https://comfort-works.com/en/content/how-to-measure-sofa-for-a-custom-made-slipcover-68 For more specific instructions, it will have to depend on your sofa's structure in which case please get in touch with us via info@comfortworks.com.au Speak soon!