Netflix told ME! Netflix offers these guidelines for what it takes to stream:
https://help.netflix.com/en/node/306
0.5 Megabits per second - Required broadband connection speed
1.5 Megabits per second - Recommended broadband connection speed
3.0 Megabits per second - Recommended for SD quality
5.0 Megabits per second - Recommended for HD quality
25 Megabits per second - Recommended for Ultra HD quality
So, if you don't have a 4K TV and 4K routed through whatever devices you're connecting to your TV, or aren't watching on a 4K monitor, you really only need 5 Mbps.
Per movie, that is, and so with 16 Mbps you'd have the bandwidth to watch 3 HD movies at a time.
Netflix offers their own version of speedtest.net here:
https://fast.com/
This is only download speeds, but it's from Netflix's locations, so it's testing the speed from Netflix.