Thanks, Dion. We delivered strong results in Q1 with impressive revenue growth and year-over-year increases in operating profit dollars, free cash flow and earnings per share.
Before getting into specific Q1 performance, I want to first provide some context on tax reform and its impact on our results. There are many broad and complex elements to the Tax Cuts and Jobs Act that require extensive tax analysis, much of which is ongoing as government authorities share further clarifying publications. We expect additional details to be available in the months ahead, so on today's call, I'll highlight the largest impact areas and provisional adjustment. I'll then later summarize the combination of these impacts in our financial outlook.
For starters, we recorded a noncash tax-related accounting gain of $1.1 billion in our Q1 GAAP-only results. This $1.1 billion gain is a net number, inclusive of the expected repatriation transition tax charge and other net accounting benefits. Under the new tax code, U.S. companies are required to pay a repatriation transition tax on offshore earnings that have not been previously repatriated to the U.S. We booked a gross repatriation charge of $3.2 billion with payments to be made over the published 8-year schedule. However, the actual cash payments will likely be much lower as we expect to reduce the overall liability by more than half once existing and future credits and other balance sheet attributes are used.
We've also recorded a net $4.3 billion accounting benefit in the quarter, which more than offsets the gross repatriation tax. This provisional adjustment is a result of reversing previously accrued-upon earnings from foreign subsidiaries, which are netted against revaluing our deferred tax assets and liabilities at a lower 21% U.S. tax rate.
In Q1, we also saw a positive impact on our effective tax rate. Our non-GAAP tax rate was 15% compared to our previously provided guidance range of 21% to 22%. The 6.5 point tax rate delta generated approximately $0.04 of non-GAAP diluted net earnings per share in the quarter.
With this context in mind, let me now cover the Q1 results. Net revenue was $14.5 billion, up 14% year-over-year as reported or 13% in constant currency. And our performance remained strong across businesses and geographies. Regionally, year-over-year, Americas grew 10%, EMEA was up 13% and APJ grew 18%, all in constant currency. Gross margin of 17.8% was up 10 basis points year-over-year, driven by improved rate in Printing, partially offset by higher commodity cost in Personal Systems. Gross margins were down 30 basis point sequentially in line with normal seasonality. Non-GAAP operating expenses of $1.6 billion were up 17% year-over-year or 5% sequentially driven by the addition of S-Print along with incremental R&D and go-to-market investments to support growth.
Net OI&E expense was $66 million for the quarter. With a non-GAAP tax rate of 15% and a diluted share count of approximately 1.7 billion shares, we delivered non-GAAP diluted net earnings per share of $0.48 or $0.44 when adjusting for the previously estimated 21% to 22% tax rate compared to the 15% recorded.
Non-GAAP diluted net earnings per share primarily excludes restructuring and other charges of $31 million, acquisition-related charges of $42 million, amortization of intangible assets of $20 million, partially offset by nonoperating retirement-related credits of $56 million and the related tax impact on these charges. Most significantly, we recorded a provisional $1.1 billion net gain for the adjustments resulting from the U.S. tax reform. In Q1, GAAP diluted net earnings per share was $1.16.
Turning to the segments. Personal Systems net revenue remained very strong, delivering $9.4 billion, up 15% year-over-year as reported or 13% in constant currency. The results continue to be broad based, reflecting our innovative product portfolio and global execution.
By customer segment, Consumer revenue was up 13% and Commercial revenue was up 16% year-over-year. By product category, Notebooks were up 14%, Desktops up 17% and Workstations up 11% year-over-year.
Personal Systems operating profit dollars grew year-over-year and operating margin was 3.6% in the quarter, which is down 20 basis points sequentially and year-over-year. We saw industry-wide increases in component costs again in Q1 driven primarily by DRAM, which continues to put pressure on margin. We now expect to see increased component costs throughout FY '18 and, therefore, are mitigating via pricing, supply chain scale and leveraging our balance sheet, driving positive mix shifts and currency favorability. Together, these actions should enable us to offset some of the commodity cost increases.
Before turning to Printing, let me add a little more color on S-Print since our financials include a full quarter of results. As a reminder, last quarter, we updated our full year FY '18 guidance to include the operational impact of the acquisition. We estimated $1.4 billion of revenue and added $0.01 of non-GAAP net earnings per share to our full year outlook.
We highlighted that, as expected, S-Print's hardware and Supplies revenue base was in decline driven by low-end A-4 products. We also describe that S-Print would be in investment mode during the first half of the fiscal year, putting pressure on overall Print margins before becoming profitable during the second half.
It's important to reemphasize that we intend to integrate the business across the globe as quickly as possible. This is fundamental to our value-creation plan and includes rationalizing SKUs with 25% of Samsung-branded SKUs already reduced by the end of Q1, combining the respective Samsung and HP-branded products into an integrated portfolio for our collective sales force, and transitioning the S-Print installed base into the HP sales model. The faster we integrate, the quicker we create value, and this is exactly our plan.
A direct result of this integration strategy is that we are unable to accurately size organic versus inorganic hardware units or revenue results. Said differently, depending on the actual tradeoffs already being made in the field, the additional $1.4 billion of acquisition revenue in FY '18 may indeed come from either Samsung or HP-branded SKUs.
From a reporting perspective, we have included all S-Print hardware in Commercial hardware revenue and units since the integration is being led by our office business. As a result, there is no impact to Consumer hardware revenue or units at this time. In the future, we may realign these SKU-level results depending on the organizational ownership at that time.
Now getting back to Printing performance. Revenue was $5.1 billion in the quarter, up 14% year-over-year or up over $600 million. We're very pleased with this growth with or without the impact from S-Print. Total hardware units were up 14% year-over-year with Consumer units up 7% and Commercial units up 73%. In calendar Q4, overall Print unit share was 38%, down 2 points year-over-year.
Moving to Q1 Supplies performance. Revenue of $3.4 billion was up 10% year-over-year, which includes approximately 6 points of S-Print supplies. We do not anticipate breaking out S-Print's specific Supplies results in future quarters due to the integration progress that has already been made and, specifically, the impact that hardware unit placements in Q1 would have on future supplies.
Overall, our Supplies results reflect our sustained efforts around stabilizing supplies and an easier year-over-year compare. We believe that the Four Box Model remains a good predictor of our Supplies performance, and we continue to operate below our channel inventory ceiling. We're in the early days of A3 but remain confident and optimistic about the opportunity ahead. An important marker for success of A3 and for our S-Print acquisition is making steady progress towards our goal of achieving at least 12% market share of A3 hardware units by the end of fiscal '20.
In calendar Q4, we achieved 7.9% total share, including both S-Print and HP. We also continue to make progress in our contractual offerings, including good momentum with Instant Ink, where we are growing our global subscriber base.
Print operating profit dollars grew $87 million year-over-year, and operating margin was 15.8% in the quarter, down 20 basis points year-over-year and 80 basis point sequentially. The largest driver of the margin decline is the impact of adding S-Print. We expect that our Q1 operating margin rate will be the low for the year.
Now turning to cash flow and capital allocation. Cash flow from operations was $996 million and free cash flow was $977 million in the quarter. We finished Q1 with a $1.2 billion net debt position, which includes the approximately $1 billion in funding for S-Print. Cash conversion cycle was minus 27 days, which weakened 3 days sequentially driven by an 8-day decrease in days payable outstanding, offset by a 2-day decrease in days sales outstanding and a 3-day decrease in days of inventory. We have been deliberately building our owned inventory and accounts payable balance steadily in FY '17 and specifically in Q4 as we leveraged our balance sheet to address rising component costs and to support growth. In Q1, we typically adjust these balances down for seasonality, and we shifted more this year, given the higher beginning balances.
During Q1, we had a total capital return of $692 million through $462 million in share repurchases and $230 million in cash dividends. With tax reform, our long-term capital allocation strategy remains unchanged. However, we will now have the opportunity to more efficiently access our global cash and run the business with lower levels of cash on the balance sheet. We are still finalizing the specific timing and quantity of repatriated cash, and we'll update you more in the months to come.
In addition to supporting operating cash needs, our priorities for using this cash are, first, ensuring that we maintain our existing investment-grade credit rating. We plan to reduce our gross debt levels, taking into consideration our resulting net debt position after repatriation, the tax repatriation, cash liability and share repurchases.
Second, opportunistically returning capital to shareholders with a focus on incremental share repurchase. Third, investing in our nonexecutive workforce as Dion described. And finally, we're not changing our disciplined and returns-based approach to capital allocation, including M&A.
Looking forward, keep the following in mind related to our financial outlook: In Personal Systems, we now expect that the overall cost of components driven primarily by memory will continue to increase throughout FY '18. This headwind and any net impact on repricing will ultimately depend upon actual market demand and competitive dynamics, including offsets from gross currency benefits.
In Printing, we expect that Samsung-branded supplies continue to decrease due to declines in the historical installed base. Overall, we expect that total Supplies revenue, inclusive of both legacy HP and S-Print, to be up 5% to 7% in constant currency for the aggregate remainder of FY '18. Looking forward to FY '19, we expect the overall Supplies business to be flat to slightly up in constant currency. In addition, we expect to opportunistically place units with a positive NPV.
For the full year, we expect to deliver our productivity initiatives as guided at SAM. We also continue to look at opportunities to take cost out of the business, especially with the close of S-Print, overall commodity cost environment and the opportunity to expand the TAM of positive NPV units. We'll also continue to leverage our balance sheet if we see attractive economic opportunities to do so.
We have factored in the various tax reform implications in our full year non-GAAP outlook. We estimate our go-forward effective tax rate to be 16% plus or minus 2 points, which is improved from our previously guided FY '18 tax rate between 21% to 22%. This generates a full year diluted net earnings per share benefit of approximately $0.13, of which $0.04 has already been earned in Q1.
Importantly, the 16% rate plus or minus 2 points is a full year outlook. We are likely to see more quarterly variations to the rate just like we saw in the lower Q1 15% rate, which is now expected to create a sequential tax headwind in Q2.
Partially offsetting the $0.13 full year diluted net earnings per share tax benefit is an approximately $0.03 diluted net earnings per share investment during the remainder of the year to fund the higher variable performance bonus opportunities for nonexecutives, which will be recorded in the segment's operating results. Therefore, the net U.S. tax reform benefit is approximately $0.10 per share for the full year with approximately a $0.02 benefit in each remaining quarter in FY '18.
From a GAAP-only perspective, our guidance now includes an incremental noncash $20 million charge per quarter for amortization of intangibles related to the S-Print acquisition. We have not assumed other GAAP-only adjustments related to the U.S. tax act other than the onetime $1.1 billion accounting gain already recorded in Q1. However, our tax analysis is ongoing and tax guidance is still being regularly clarified by government authorities, which may impact our go-forward tax model or accounting and, therefore, result in future adjustments.
With all that in mind, we expect Q2 '18 non-GAAP diluted net earnings per share is in the range of $0.45 to $0.49, including the $0.02 net benefit from U.S. tax reform. Q2 '18 GAAP diluted net earnings per share is in the range of $0.42 to $0.46.
We are raising our full year fiscal '18 non-GAAP diluted net earnings per share by $0.15, including the $0.10 net benefit from U.S. tax reform. The range is now $1.90 to $2. And our full year fiscal '18 GAAP diluted net earnings per share is in the range of $2.53 to $2.63.
Before transitioning to Q&A, I want to update you on prospective changes to our earnings calendar. We're looking to move our earnings calls in future quarters closer to the date of quarterly or annual reports with the SEC. The changes in the number of dates will depend on the specific quarter, and we'll continue to announce our earnings call dates about 2 weeks prior to each call.
I know there are a few new and somewhat complicated topics that we covered, so let me briefly summarize our quarter. We had impressive revenue growth and year-over-year operating profit dollar expansion across both segments with or without S-Print. We continue to make progress executing our core growth and future strategy. And we're investing in the business for the long term and, at the same time, committing to return capital to shareholders.
With that, let's open up the call for questions.