Measure ASP.NET page load time

I'm currently developing an ASP.NET application which uses a MasterPage and I want to measure my application webform's loading time and display that information to the client.

My current strategy involves using the Application_BeginRequest event associated callback (in the Global.asax file of my website solution), to start the measurement of the time spent on the server-side process (as follows)

protected void Application_BeginRequest(Object sender, EventArgs e) {
   Context.Items.Add("Request_Start_Time", DateTime.Now);
}

and calculate the elapsed time on the webform's OnPreRender event associated callback, printing it on a placeholder element (as follows)

protected override void OnPreRender(EventArgs e) {
   base.OnPreRender(e);

   TimeSpan tsDuration = DateTime.Now.Subtract((DateTime)Context.Items["Request_Start_Time"]);
   ExecutionTime.InnerHtml = "<em>Server-side processing duration: " + tsDuration.TotalMilliseconds + " miliseconds.</em>";
}

is this the best way to measure loading time? Is there a more "elegant" way to accomplish this?

Thanks in advance for your time and cooperation.