Fertility Awareness Method for Natural Birth Control: Getting Started
There are a lot of different apps and chart tracking websites available for those who don't want to do paper charts, but you have to be very careful about which ones you use — and how much you depend on their calculation of ovulation days — if you are trying to avoid a pregnancy.
I use the Fertility Friend website. I have tried the app but can't get it to work on any of my devices. FF has a disclaimer right on the site that you shouldn't use it if you are trying to avoid a pregnancy. The reason for this is because the FF charts guess (pretty much blindly) at your ovulation day. If you are trying to get pregnant, it's not a big deal for it to be off a few days (in my experience it seems to almost always pin ovulation a few days before it actually occurs). However, for those trying not to get pregnant, this would lead them to believe that ovulation occurred before it actually did, showing them in the safe post-ovulation days too early. This is a big problem.
That doesn’t mean you have to chart by hand, however. I input all of my data into the FF charts, and then pay no attention to when it tells me ovulation is. Once I see where it is on my chart by my own interpretation, I go in and override the ovulation day and coverline.
Taking Charge of Your Fertility — a must-have book for all women — does have a companion site where you can use their software. I don't have personal experience with this one, because it is not free, but I have heard great things from the trying-to-avoid crowd.
These are usually use at your own risk. Many simply document when you start and end a period, giving you little to no information on your fertility. If you want to use this option, look for an app that let's you track basal temperatures, cervix position and cervical fluid at a bare minimum, and always do your own chart interpretations.
Using some 0.99 app from the Google Play store and thinking you are going to get reliable interpretation of your fertility signs is a good way to get knocked up.
Have you used any charting software or apps? Anyone prefer to do paper charts?