It is estimated that an average website user waits for a maximum of 5 seconds before leaving the website if it has not loaded.
To check your website speed click here https://tools.pingdom.com/, type in your URL and the country where the bulk of your customers come from.
Once you have started your test it will scan your website and give you a score.
In there is will say load time, page size and performance grade. The performance grade is a good indicator on how well your website is loading compared to others and is good information to go to your hosting provider with.