I personally chart on Fertilityfriend.com and have done for many years. I find their site very useful and they also have a free app. Their basic membership is free (which I use and find sufficient) but you can pay for a premium membership if you wish to.
If you can chart online please register to the site below. You will be given a unique profile number and link to your chart that way if you ever need any help working out when you ovulated or how to understand your chart you can give me that link (There are options to change what others can see on your chart).