Stephen Vintz
Analyst · Deutsche Bank
Thanks, Amit. Let me now dive deeper into Tenable's second quarter 2018 financial results and our business outlook.
I'll begin by mentioning that except for revenue results, which are GAAP, all financial results we will discuss today are non-GAAP, unless otherwise stated. As Andrea mentioned at the start of the call, GAAP to non-GAAP reconciliations of these financial measures can be found in our earnings press release issued earlier today.
I would also like to remind you that we included ranges for preliminary results for Q2 revenue, calculated current billings and non-GAAP loss from operations in our IPO prospectus in July, just prior to our roadshow. That said, I'll start my review of the quarter with the income statement.
Revenue for the quarter was $63.6 million, representing a 44% increase over the same quarter last year, which is a testament to the growing strategic importance of VM and the broader Cyber Exposure mandate.
It's also worth noting, our growth and scale are driven by our recurring revenue, which we expect will continue to track in the 85% to 90% range going forward. Please note that when we refer to recurring revenue, we include revenue from subscription and maintenance contracts and exclude revenue related to professional services and perpetual licenses as such amounts are not available for renewal.
Before we move off revenue, let me cover the highlights of our adoption of ASC 606 in 2017. First, the revenue presented herein reflects the adoption of 606 on January 1, 2017, on a modified retrospective basis. So the year-over-year comparisons are on the same basis. Second, under 606, revenue from perpetual licenses is recognized over 5 years. And finally, sales commission expense is deferred over periods ranging from 3 to 5 years based on product. Commissions are amortized over 5 years for perpetual licenses, 4 years for enterprise subscription sales and 3 years for Nessus sales.
With regard to sales, we sell our software primarily on an annual subscription basis, with a term that is generally 1 year in length, although some customers prefer multiyear contracts. Substantially, all of our contracts are paid upfront. The value of a contract can vary based on the number of IPs or assets purchased. Now with that as a backdrop, I want to walk you through our calculated current billings. Since swings in the percentage of billings from multiyear prepaid contracts can meaningfully skew growth in total billings higher or lower in a given period, we believe calculated current billings is a better proxy of the underlying momentum of the business and the closest corollary to annual contract value, which is how we manage the business. Calculated current billings, defined as the change in current deferred revenue plus revenue recognized in a period, grew 39% on a year-over-year basis to $77.4 million in the second quarter of 2018. This is above the estimated range of $76 million to $77 million included in the IPO prospectus. If you're attempting to calculate current billings in 2017, you should note it was impacted by the adoption of 606. As a result, you need to add $19 million to the current deferred revenue to the balance at December 31, 2016. For more information on how we calculate this metric, please see our IPO prospectus and our press release.
Let's move forward and discuss what is driving the growth in billings for Tenable. First is new customers. As Amit said earlier, we added 282 new enterprise customers in the second quarter, which is up from 30% from 217 in the same period last year.
The number of new enterprise logos is a clear indication of the lofty of new business and the untapped demand we are seeing worldwide for our software solutions.
Now let's talk about expansion from existing customers. While we're adding new enterprise customers at a fast pace, equally important is the fact that we are growing the value of those relationships. At the end of the quarter, we had 340 customers spending in excess of $100,000 in annual recurring revenue on an LTM basis, which represents an 88% increase over the same period last year. Our momentum in customer acquisition and expansion is a testament to our go-to-market approach, which provides multiple ways to land and expand. Many of our enterprise customers initially become aware of Tenable through Nessus, which is one of the most iconic and beloved brands in security. We have approximately 2 million downloads of our free version of Nessus and approximately 19,000 customers on our paid version of Nessus. The paying Nessus customers directly contribute less than 25% of our total billings. But even more important is the fact that they service and on-ramp through a larger enterprise platform sale, which is the majority of our business. 1/3 of all of our enterprise platform sales have historically come from Nessus upsells. We believe this is a major competitive advantage that no one will be able to replicate, given the rich history and ubiquitous nature of Nessus.
Now that you understand our go-to-market strategy a little better and how we land new deals from either a low, no or high touch sales motion, let's dive deeper into customer expansion. We have a customer success organization that leads the charge of renewals and aids in upsells, which has culminated in dollar-based net expansion rates to have historically been in the 120% or better range. We utilize the dollar base net expansion rate to measure the long-term value of our customer relationships because it is driven by our ability to retain and expand the revenue generated from our existing customers. As a public company, we plan to share when our dollar base net expansion rate significantly differs from 120%. For more information on how we calculate this metric, again, please see our IPO prospectus.
Let's talk about our pricing model so you understand how we can upsell an existing enterprise customer. It happens one of 2 ways. First, we have an asset-based pricing model. So in a market where there is a growing number of network-connected devices each year, we naturally grow with our customers as they look to secure more assets. Second, an increasingly complex IT environment has resulted in new attack vectors, causing customers to secure new types of assets, which we think will drive adoption of new modules for Tenable. We believe we could build a very large business by simply continuing to expand with existing customers.
Now I'll turn to expenses and profitability. Non-GAAP gross margin for the quarter was 85%. We expect gross margins will trend down to the low 80s, high 70% range over time as a result of our investments in building out Tenable.io on a global basis.
Now turning to operating expenses. We are focused on improving leverage in our business over the long term, but in the near term, we are investing in growth. To provide some historical context, the company did not raise any primary institutional capital prior to the IPO, which speaks to the capital efficiency of our business model. We have seen the positive results of increased investments in our business over the last few years as growth has accelerated from 2015 to 2018.
It was a conscious decision to trade points of margin for points of growth. We believe we can execute on this plan while driving the business to cash flow breakeven by the end of 2020.
Sales and marketing expense for Q2 were $41.2 million compared to $27.4 million in the second quarter last year. This represents 65% of total revenue versus 62% of total revenue in Q2 last year. The high percentage reflects increased investments in building our global sales organization. There is obviously an upfront cost while the payback occurs over time.
Our compelling market opportunity and our dollar renewal rates give us confidence to continue to invest here. R&D expense in Q2 was $17.2 million compared to $13.3 million in Q2 last year.
As a percent of total revenue, R&D was 27% in Q2 versus 30% in Q2 last year. Innovation remains a top priority for us, especially around the new paradigm in data analytics and benchmarking, we will continue to invest in, in R&D for the foreseeable future.
G&A expense was $8.9 million for the quarter compared to $5.6 million last year. As a percent of total revenue, G&A was 14% in Q2 versus 13% in Q2 of 2017. The increase reflects our investments associated with preparing for our move to the public markets. Our non-GAAP loss from operations in the quarter was $13.3 million, better than our preliminary estimated range of $15.2 million to $14.2 million included in the IPO prospectus and compared to a loss of $7.2 million in the second quarter of last year. Non-GAAP operating margin was negative 21% compared to negative 16% in the second quarter last year. Pro forma non-GAAP loss per share was $0.18 compared to a loss of $0.09 in the same period last year.
The pro forma weighted average shares assume the preferred shares were converted into common for all prior periods. As a reminder, we are using pro forma shares for the forecast and historical periods solely for comparability purposes. All of our preferred shares converted into common shares at the IPO in July. We finished the second quarter with $23.7 million in cash. However, this does not include the $265 million in net proceeds raised from our IPO in July. Our free cash flow burn was relatively modest at $1.1 million for the quarter, which is generally consistent with the second quarter of 2017.
Going forward, we expect our free cash flow burn to modestly increase in the near term as we continue to invest in the business and absorb increased costs associated with becoming a public company. Again, we have a highly efficient business model, and we believe we will return to profitability over time. That said, with the returns we are generating on our investments and the opportunity to win a major security market, we believe that the right strategic decision is to maintain a higher level of investment in the near term.
Now turning to guidance. For Q3 2018, we currently expect revenue to be in the range of $66.0 million to $66.5 million. We expect non-GAAP loss from operations to be in the range of $17.5 million to $16.5 million, non-GAAP net loss in the range of $17.1 million to $16.1 million and pro forma non-GAAP net loss per share in the range of $0.19 to $0.18 a share, assuming a weighted average shares outstanding of 88.7 million.
For the full year 2018, we currently expect revenue of $260 million to $261 million. We are also providing annual guidance on calculated current billings, and we'll update this, when appropriate, at the end of each quarter. For the full year of 2018, we expect calculated current billings of $314 million to $316 million, which compares to $235.6 million for the full year 2017, non-GAAP loss from operations in the range of $60.7 million to $58.7 million. We also expect non-GAAP net loss in the range of $61.2 million to $59.2 million and pro forma non-GAAP net loss per share in the range of $0.72 to $0.70 a share, assuming weighted average shares outstanding of 84.8 million.
In closing, our confidence in driving our Cyber Exposure vision is bolstered by an attractive market opportunity in front of us. We look forward to continuing the dialogue with all of you.
And now let me turn the call back to Amit for some closing comments.