What is the average size of an Elastic Beat, ElasticSearch document?

I currently do a small research to know what kind of server I need.

Currently the only thing (for now) I need to calculate the average size of an Elastic Beat.

The Beats I will use are:

• Metric Beat (System data, Nginx, MySQL and Apache)
• Heart Beat
• File Beat (Apache2, Nginx and MySQL)

My question is:
Is there any way I can measure the average size of an Elastic Beat document, without needing to install Beats somewhere?

I tried the same and had to install and use it for a week. The problem is, that the beats are clever enough to only send changes - so it heavily depends on your servers and their load on how big the documents are.