20 photo messages and audios consume almost 2 Mega.
Browse the feed for 5 minutes, it spends around 2 Mega. In Facebook settings, you can activate data saving mode
To upload 5 photos, the consumption is about 2 Mega. In the app itself, you can activate "Use less data" to reduce expenses.
In the lowest quality, consumption is 26 Mega every 15 minutes.
Using the app for 5 minutes consumes about 8 Mega. You can activate the "Data Saving" option in the app it self.
On average, you spend 0.7 Mega per page, but it all depends on the type of website you are going to access. In reading mode, you consume less data.
To save data consumption, it is recommended to adjust the video settings to medium resolution (480p), so you will save and enjoy your internet more.
To listen to music online the consumption is about 3 Mega per minute.