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How fast should my Internet connection be to watch streaming HD movies?

Internet Speed and Bandwidth for HD Video Quality
Web sites like offer free tests of your Internet connection's current upload and download speeds.
Screenshot by Stephanie Crawford for HowStuffWorks

In a 2010 survey, the Federal Communications Commission (FCC) found that 80 percent of people with broadband Internet in the U.S. didn't know the speed of that broadband connection [source: Gurin]. In addition, some may be surprised to learn that they're only getting a fraction of their service's advertised maximum speeds. For example, your Internet service provider (ISP) might have you on a plan that says "up to 30 Mbps down" while you're really only getting download speeds of around 19 Mbps.

Web sites like offer free tests for both the upload and download speeds of your Internet connection, but be cautious of some of the tempting "start" buttons in ads on the sites -- many are actually well-designed ads that look like they're part of the site's test mechanisms. Before you call your ISP about any discrepancies, remember that the plan you're on is based on a maximum value. Your actual results are affected by factors like your ISP's peak Web use times, the number of people sharing your line and your distance from the ISP's fiber pipeline.

When it comes to streaming HD video, you'll need a broadband speed, or bitrate, that's capable of handling a progressive scan rate of 720p. Since your HD-capable screen is refreshing the screen 60 times per second, this means ensuring that all those video frames are received and ready to play before they're needed. Your computer or other device will cache all the incoming data and queue the video frames so they're ready for smooth playback.

From there, determining the speed you'll need seems to be a matter of math. That math, though, requires some idea about the size of the video file. This depends on how the file is encoded, more commonly referred to as the file type. A one-hour 720p video in the MPEG-2 standard might be 2.7 GB while the same video in one of the newest video standards, H.264/Advanced Video Coding (AVC), could be almost 13 GB [source: Digital Rebellion]. Thus, differences in file size could be one explanation for why different Web sites have different speed recommendations for streaming their HD content.

Suppose the video you're streaming is one hour long, and the file size for that video is 6 GB. While a broadband connection of up to 10 Mbps lets you easily stream a lot of video content online, you'll want 15 Mbps or more for this six-gigabyte HD video. Here's a quick look at the math:

  • Megabits per hour calculation: 49,152 / 3,600 = 13.65 Mbps

When you're streaming HD content, also consider whether the connection jumps over a wireless router. If so, note that the connection speed could drop over the connection if the WiFi standard isn't fast enough. You'll want to avoid slower 802.11b connections, and the newest 802.11n is the ideal choice to keep up with faster broadband services.

As with anything you do over your broadband connection, be sure to note whether your ISP will slow down or stop your service after reaching a certain bandwidth threshold. Some sites, such as Netflix, let you choose a lower playback quality to help you stay within those thresholds, even though it means giving up the higher definition. Also, make sure the hardware you're using isn't just HD-capable, but it has the processing power to cache and play video files in HD.

For lots more information about your internet connection and streaming HD video, head on over to the next page.