If you invest in Bitcoin and want to keep a track of your investments then the simplest way is to install a portfolio tracker app. This will allow you to record any buys and sells of a particular trade on a selected exchange and from that point on it will track your profits or losses.
The free apps are very useful in allowing you to track the portfolio value in either FIAT or bitcoin, show price charts, calculate your % holdings and display price changes. One of their best features is allowing you to set alerts on prices of bitcoin if you want prompting to buy or sell at a set price.
The two most popular apps we recommend are:
IOS/Android
IOS/Android/Windows/Mac
We recommend downloading and trialing both, choose the one you prefer and then record all of your trades with it from that point on. You will then have an historic record of all of your trades which is very important data when investing.
You also have the ability, using the applications inbuilt keys to copy and backup the portfolio data to a new mobile or tablet if ever necessary.