What's correct way to measure website / webpage load timing

I tried searching for this answer but couldn't get exact one.

As of my current knowledge there are 2 ways to measure webpage / website load timing

• complete webpage / website is loaded ( total time shown in waterfall in chrome console )

• OR in waterfall graph of google console take first document load timing only ( this is normally the url of the webpage )

I need to capture this data on regular basis. As QA for me I should capture time taken by all the components in waterfall but from Developer side, s/he says only first element in waterfall is important.