What Is the Speed of a T3 Connection?

By Josh Fredman

T3 Internet service conjures images of speed, elegance and elite service. Only large institutions can afford it, and the speeds are lightning fast -- some of the fastest available. In fact, the very first backbone of the Internet back in the 1980s was actually a lower-speed T1 line. T3 service comes on a dedicated, leased line -- usually fiberoptic, or else copper -- which is even more crucial to business customers than its speed.

An Overview of the T-Carrier System

You can think of a T3 line as 672 telephone voice lines all tied together, because that's what it originally was. Back in the 1950s and 60s, AT&T developed the T-Carrier system as a cost-effective way to handle telephone calls within large cities. The lowest T-Carrier system, T1, consists of 24 individual lines multiplexed together, and the T3 system consists of 28 T1 lines, for a total of 672. T-Carrier lines are digital rather than analog, and when they were introduced they eventually appealed to organizations who sought to use T-Carrier lines for data transfer, which is their primary purpose today.

T3 Data Transfer Speed Comparisons

T3 data lines have a specific data transfer rate of 44.736 megabits per second, with a little bit shaved off for the technical requirements of maintaining the system. At that speed you could download a 700MB video in a little over 2 minutes, or a 20MB music file in about 4 seconds. For comparison, a typical residential cable or DSL download speed tends to run between 3 and 15 megabits per second, and average 4G wireless download speeds are similar to that. That means that with a T3 connection your download speeds will average between 2 and 20 times faster.

T3 Uploads

Getting download speeds that fast sounds good, but it pales in comparison to the history of T3. Back in the 1990s and early 2000s, T3 was thousands of times faster than a typical dial-up modem connection. This is still reflected in the comparison of upload speeds: The T3 upload rate is 44.736 megabits per second, just like the download rate. This is due to the T-Carrier system's original purpose as a telephone system, where users needed to be able to both speak and listen at the same time. By way of contrast, the average American upload speed is roughly 600 kilobits per second, making T3 about 75 times faster for uploads.

T3 Customers and Pricing

T3 customers have traditionally been large organizations like corporations and universities that want ultra-fast data transfer speeds both on their local networks and when accessing the Internet. The T3 lines also typically handle the organization's telephone system, just as originally intended. As of the 2010s, newer broadband technologies like DSL and cable can vastly outpace the slower T1 lines and can even compete with T3, but organizations often still utilize T-Carrier service because of the guaranteed bandwidth and uptime -- a crucial detail for mission-critical operations. The price for constant uptime on a dedicate circuit is steep: T3 service typically costs several thousand dollars a month.