If you visit the page for your OneDrive for Business, you’ll notice a COG in the top right hand corner of the window as shown.
If you select that, you’ll see a menu like shown above. Select the OneDrive settings option as shown.
Here you’ll find a page with a whole lot more options. In this case select the option, Storage metrics as shown.
You should also note that there is a Run sharing report option as here well.
The Storage metrics option allows you to see a breakdown of the data storage in your OneDrive for Business as shown. You’ll also notice in the top right, the total and used capacity of your data.
You can drill further into directories by simply clicking on them. The above shows the data break down in the Documents directory below the OneDrive for Business home location.
Microsoft will also be adding more options to the COG over time so make you check there regularly.