Bandwidth vs. Throughput: What is the Difference?
Discover why your actual download speeds never quite match the advertised bandwidth of your internet plan, and how throughput reveals the truth.
Theoretical Capacity vs. Reality
If you pay for a 500 Mbps internet plan, you expect to download files at exactly 500 Mbps. However, if you monitor your task manager during a large download, you will notice the speed maxes out somewhat lower than that. This discrepancy is the difference between bandwidth and throughput.
Bandwidth is the maximum theoretical capacity of your network link. Throughput is the actual, real-world amount of usable data that successfully arrives at its destination in a given time period.
The Cost of Overhead
Why is throughput always lower than bandwidth? The answer is protocol overhead. When a server sends a picture to your phone, it cannot just send raw pixels. It must package those pixels into TCP packets, wrap them in IP headers, and encapsulate them in Ethernet frames.
All of this packaging requires extra data. In a typical network transfer, about 5 to 10 percent of your bandwidth is consumed entirely by these invisible headers. Furthermore, if a packet gets lost during transmission and has to be resent, that wastes even more of your theoretical bandwidth, further lowering your actual throughput.
Why This Affects Your Speed Test
Our speed test measures throughput, not raw theoretical bandwidth. We measure the actual file data that successfully reached your browser. Because of this, even on a perfect fiber connection with zero congestion, your speed test result will inherently be slightly lower than your advertised plan speed.
If you pay for 1000 Mbps, seeing a result of 940 Mbps is actually a perfect score. The missing 60 Mbps is the necessary protocol overhead keeping the internet functioning.