Data Usage Guide – How Much Data Does a VPN Actually Use?

The whole idea behind using a VPN is to keep your private data private. But just because you hide your confidential information from snoopers doesn’t mean it disappears. The computers still count your data as it passes through, even if it doesn’t know a lot about what’s in it. It reminds me of the old amusement park turnstiles I passed through when I was a kid. (You could make your way through and then take the time to tell your brother that you were the 234,892nd person to go through.) ISPs count every time a data packet goes through, and they do that because they make money from it. The more data, the more money. And users need to keep track of the data they use so they can save money. But don’t count on a VPN helping you in that respect.

What Is Data?

It may seem like a silly question with an obvious answer, but if data usage determines how much money is spent, we’d all better be sure we know what it is. According to TechTarget, “In computing, data is information that has been translated into a form that is efficient for movement or processing.” And what is that form? Binary numbers. We’re talking about bits and bytes here. Bit is another word for a binary digit — meaning either a 0 or a 1. A byte is eight bits.

So let’s look at an example. Take the word “Hello.” Here you see that the word when written in binary come out to 40 bits, or 5 bytes.

Hello 01101000 01100101 01101100 01101100 01101111


Every bit of information (an appropriate phrase) that you send or receive on the internet, you are transmitting in bits. But you should also know that bytes — rather than bits — is the normal unit for measuring data.. On a larger scale, you would measure data in kilobytes (KB), or megabytes (MB), or gigabytes (GB). or terabytes (TB).

Note these examples of data traffic. The first one shows data passing through my laptop, and the second one shows a history of data that has passed through my smartphone.

wifi vpn data usage

mobile vpn data

VPN Data Is Still Data

The point of all this discussion about data is to make it clear that — no matter how hard you try to disguise it — any counters that track data will include VPN data transmission. Don’t expect VPN to jump over the turnstiles. It’s still data, and internet service providers (ISPs) will still count it as such. There is nothing special about VPN that would exclude it from this accounting. It is still made up of bits and bytes. It is still data. Using a VPN will not help you avoid ISP and mobile caps.

Just as a reminder, a virtual private network can do many helpful things for users. It can protect data from attack or unwanted surveillance. It can bypass geographical restrictions for those wanting to access their subscription services while traveling. It can tunnel through public networks and create a private environment as if you were on your home or company local area network. But it can’t fool an ISP into thinking that it’s not data.

In general, ISPs handle VPN traffic much the same as any other traffic. It is data, and you will have to pay for it according to the plan that you’ve selected with your ISP.

ISP Zero Rating and Deep Packet Inspection

Now, we should point out here that some ISPs do view data differently. Using a practice known as zero rating, some internet providers let you stream data, such as YouTube, at no additional cost. But what happens if you are streaming this service through your VPN? This may very well abnegate the potential savings by putting the data back into the regular pool of non-zero-rating data. “Using a VPN could in theory level the playing field by bringing a zero-rated site or service back into one’s standard data plan,” says an author for ExpressVPN. On the other hand, any streaming service that the ISP throttles will not affect you within your safe and secure VPN tunnel — which is a good thing.

How does an ISP know what kind of data you are using? If you are on a VPN, they don’t. But without a VPN, your ISP could detect what you are doing with your data. An article from TechRepublic explains why deep packet inspection matters:  “Deep packet inspection illuminates network trends, helps ISPs optimize bandwidth and throughput, and can reveal user behavior.” The problem of ISPs and data inspection is one that every concerned internet user should learn more about.

Does VPN Use More Data?

The short answer is yes. It takes more data to transmit a secure VPN channel because the technology is entirely dependent on encryption. And encryption requires a significant amount of processing.  How much? That depends on the type of encryption you are using. As we have discussed in our blog post on VPN protocols, every VPN application uses one or more protocols, and these protocols use different forms of encryption. The overhead required to run your VPN app depends on which encryption the software includes.

Encryption uses bits (binary digits, if you remember) to secure bits in a data stream. Both the sender and receiver of an encrypted message use encryption keys to lock the data. Obviously, an encryption technology with more bits would normally require more data processing than one with fewer bits. A cryptographic key might be 128 bits long, as in AES-128 encryption. Or it might be use 256 binary digits.

If you’ve ever worked a combination lock, you know that it takes a little time to get through the numbers. Even a simple three digit lock, like the one you might have used with your high school locker, takes a bit of mental and physical processing. You have to remember it first, and then you have to turn your fingers to each number before it will open. Now imagine how much processing it requires for a computer to process a lengthy digital encryption key. This graphic borrowed from an article in EETimes, “How secure is AES against brute force attacks?”, will give you some idea:

encrypted data possible combinations

If you really want to know how much overhead your VPN is causing you, have a look at the underlying protocol. Which encryption does it use? The more bits involved, the greater the processing cost.


So which VPN protocol should you use if your goal is low data use? Obviously, you would use the one that has the fewest processing requirements. That would probably be 128-bit PPTP. The problem is that PPTP also provides the least security among VPNs on the market. There’s definitely a trade-off between VPN data usage and level of security. On the higher end, 256-bit Stealth OpenVPN uses a lot of data but also offers very high security. In the mid-range, many people are moving to OpenVPN today, which at 128 bits has low overhead and offers moderate security. The amount of data you use not only affects your ISP bill, but It also affects the performance of your secure data stream. Whatever VPN you choose, keep in mind that there’s no free lunch when it comes to data usage.

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