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When you sign up for home internet, you often pay a certain price based on the speed of your connection. The faster it is, the more you pay. It's important to know how to check if you're getting what you pay for. You might be surprised to find that you're not, in which case a call to your internet company may be in order. I'm going to explain why internet speeds matter and show you how to check the speed of your internet connection at home. Here's what you need to know.

Why do internet speeds matter, anyway?

CNBC | Jeniece Pettitt

As streaming services like Netflix and Hulu have become more popular, and as resolutions have jumped from HD to 4K, so too has the importance of having a fast home internet connection. If you're streaming a show from Hulu and it's not coming down in high definition, or if it's constantly pausing, chances are you don't have a fast enough connection. And remember: your internet is shared across all of the connected devices in your home, so that connection is divided up between people and devices. The more people in your home using the internet at the same time — maybe a kid is playing "Fortnite" upstairs on her computer, for example, or your son is streaming Hulu on another TV — the faster internet you'll want.

How fast does my home internet speed need to be?

Netflix recommends a connection speed of 5 Mbps or faster for HD streaming, but again, that's for each device that's connected to your network. It's also awfully slow, all things considered. If your home internet is capped at 5 Mbps, then technically only one device at a time is able to stream at that speed. Cable internet speeds vary widely around the U.S. Depending on where you live and who you buy internet service from, you'll find speeds from below 1 Mbps to more than 1,000 Mbps (1 Gbps). I think most family-of four households should have at least a download speed of 50 Mbps. To put that speed in perspective, it should allow you to download a 2 GB movie in a little more than five minutes. If you pay for 1 Gbps, you could download that same movie in 16 seconds.

How do I check how fast my home internet is?

Tap go on SpeedTest.net

Now that you know why you want fast internet, it's time to make sure you're actually getting the sort of speeds that your provider promises. If you're paying $70 a month for a plan that promises up to 250 Mbps, but you're actually only getting 60 Mbps (a plan that might normally cost $40 a month), then you should call your cable company and ask for a discount or to fix your connection speed. Often, they can resync with your cable modem to make sure the speeds are faster. Here's how to check your home internet speed: Connect to your computer to your router using an Ethernet cable.

Open your web browser.

Navigate to www.speedtest.net.

Tap "Go." Speedtest.net will show you your download and upload speeds. Sometimes you might be a little below or a little above what you pay for. That's fine, but you don't want the results to be drastically below the speed you're supposed to be paying for. Internet speeds can fluctuate throughout the day, so do multiple tests to see what your connection speed averages out to.

What about on my phone?

Todd Haselton | CNBC

If you have a smartphone, you probably also pay for high-speed 4G LTE. You can download the Speedtest app for Android or iPhone to run a similar test. Unfortunately, since wireless data varies drastically on where you are when you test it, and how strong your signal is with a nearby tower, you can't really just call and have your modem reset as you would with home internet. Still, you can get a good idea of how your speed compares with your home internet, and where you get the best coverage. If you consistently see slow speeds at home, maybe it's time to find a new wireless provider.