According to the "Mythical Man Month" it's 3x to make it usable by others, and/or 3x to be a reusable component in a system (more or less), or 9x for both:
This is covered in the first 5 pages of the book, which can usually be read online from Amazon. And it jives very well with every software project I've been involved in over ~20 years.
Anyone who does software as a profession needs to have read this book. And if your manager has not - find a new manager.