Financial-technology company Square (SQ -3.84%) has seen some incredible momentum recently. In the company's third quarter, revenue soared 51% year over year and non-GAAP earnings per share jumped from $0.07 in the year-ago quarter to $0.13. Growth has been driven by continued momentum in the gross payment volume (GPV) and a growing contribution from the company's subscription and services-based products.

Investors have applauded the company's staggering growth, buying up shares in droves. The stock has risen more than 70% over the past 12 months and nearly 500% over the past two years. For investors interested in learning more about the company and what's driving its staggering growth, here are five key metrics: 

A restaurant employee interacts with Square for Restaurants platform

Square's platform for restaurants. Image source: Square.

1. Accelerating revenue growth for 6 quarters in a row

Not only has Square's top line been growing at impressive rates, but it has been accelerating sharply for six quarters in a row. Even in Square's most recent quarter, this acceleration was significant. Q3 revenue was up 51% year over year, and adjusted revenue increased 68% during this same time frame. This compares with 48% and 60% year-over-year growth, respectively, in the second quarter of 2018.

2. 41% growth in GPV from larger sellers

GPV from larger sellers, or sellers with $125,000 or more in annualized gross payment volume, increased 41% year over year. This significantly outpaced Square's year-over-year growth rate for overall GPV of 29%.

3. 24% of GPV comes from megasellers

The most impressive growth in Square's GPV in recent years has come from sellers with over $500,000 in annualized GPV. These sellers now account for 24% of Square's gross payment volume, up hugely from 16% of payment volume two years ago.

4. 155% growth in subscription and services-based revenue

A key catalyst for Square recently has been its triple-digit growth in subscription and services-based revenue. In its third quarter, this revenue was up 155% to $166 million. Adjusted subscription and services-based revenue was up 165% year over year to $172 million, accounting for 40% of total adjusted revenue.

Key drivers for this revenue were Instant Deposit, Cash Card, Caviar, Square Capital, and revenue from the recently acquired website builder Weebly and corporate catering company Zesty. Even when excluding these acquisitions, revenue from the segment increased 117% year over year.

5. 107% year-over-year growth in adjusted EBITDA

Fortunately, Square's growth story isn't all about the top line. The company's adjusted EBITDA has also risen sharply, climbing 107% year over year in Q3 to $71 million.

Looking ahead, Square expects momentum to persist. The company guided for fourth-quarter adjusted revenue of $446 million to $451 million. The midpoint of this guidance range represents 59% year-over-year growth.