In the first quarter, we had all-time record sales of almost $2.7 billion, an increase of 17% as reported or 9% on a constant basis with adjusted operating income of $329 million, our highest ever first quarter earnings per share of $3.49.
We continue to implement our restructuring plans, which have achieved $75 million of our anticipated $100 million to $110 million in savings.
In the first quarter, we purchased $123 million of our stock at an average price of $179 for a total of $686 million since we initiated our purchasing program.
Our balance sheet remains strong with net debt less short-term investments of $1.3 billion.
Sales in Q1 2021 were $2,669 billion.
That's a 17% increase as reported and 9% on a constant basis.
Gross margin was 29.7% as reported or 30.1% excluding charges, increasing from 27.5% in the prior year.
SG&A, as reported, was 17.
8% or 17.7% versus 20.3% in the prior year, both excluding charges, as we saw strong leverage on the increased volume and productivity actions, partially offset by inflation in FX.
Gives us an operating income, as reported, of 11.9% of sales.
Restructuring charges for the quarter were $11 million, and our savings, as Jeff said, are on track as we have recorded approximately $75 million of the plan.
Operating margin excluding charges of 12.3%, improving from 7.2% in the prior year or 510 basis points.
Interest expense of $15 million includes the full impact of the 2020 bond offerings.
Other income of $2 million, mainly the result of favorable transactional FX.
Our non-GAAP tax rate was 22% versus 20% in the prior year, and we expect the full year to be 21.5% to 22.5%.
Giving us an earnings per share as reported of $3.36 or excluding charges, $3.49, which is 110% improvement versus prior year.
Global Ceramic had sales of $930 million, a 10% increase as reported, or approximately 5% on a constant basis with strong geographic growth, especially in Brazil, Mexico and Russia, while the U.S. was unfavorably impacted by the February ice storm.
Operating income, excluding charges of 9.6%, that's up 400 basis points versus prior year, and this improvement was from strengthening volume and price/mix increased manufacturing uptime and productivity, partially offset by unfavorable inflation.
In Flooring North America, sales of $969 million or a 14% increase as reported or 9% on a constant basis, driven by strong residential demand with commercial beginning to recover from its trough.
Operating income excluding charges of 9.3%, that's an increase of 410 basis points versus prior year.
And finally, Flooring Rest of the World with sales of $770 million.
That's an increase of 31% as reported or 15% on a constant basis as our focus on the residential channel drove improvement across product -- all our product groups led by laminate, LVT and soft surface business in Australia and New Zealand.
The operating margin excluding charges of 20.9%, an increase of 740 basis points versus prior year, driven by the higher volume, favorable impact of price/mix and productivity, partially offset by the increase in inflation.
Corporate and eliminations came in at $11 million, and I expect for the full year 2021 to be approximately $40 million to $45 million.
Turning to the balance sheet; cash and short-term investments are approximately $1.3 billion, with free cash flow in the quarter of $145 million.
Receivables at just over $1.
8 billion, giving us a DSO improvement to 54.
4 days versus 57 days in the prior year.
Inventories were just shy of $2 billion.
That's a decrease of approximately $200 million or 9% from the prior year, with the marginal sequential increase of 4% from Q4 or approximately $80 million.
Inventory days remained historically low at 105.5 days versus almost 130 in the prior year.
Property plant equipment just over $4.4 billion with CapEx for the quarter of $115 million versus D&A of $151 million.
Full year CapEx is currently estimated at $620 million with us reevaluating our plan, and we will most likely see an increase from that level.
Full year D&A is projected to be $583 million.
And lastly, the overall balance sheet and cash flow remained very strong with gross debt of $2.7 billion.
As I said, total cash and short-term investments of over $1.3 billion, giving us a leverage of 0.9 times adjusted EBITDA.
First quarter sales of our Flooring Rest of World segment increased 31% as reported or 15% on a constant basis, exceeding our expectations.
Margins expanded over last year to approximately 21% due to higher volume, favorable price and mix and positive leverage on SG&A, partially offset by inflation.
At this point, we anticipate some material shortages continuing into the second quarter.
For the period, our Flooring North America sales increased 14% as reported or 9% on a constant basis.
Adjusted margins expanded to 9% due to higher volume, productivity gains and mix improvements, partially offset by inflation.
In the quarter, our Global Ceramic sales rose 10% as reported and 5% on a constant basis, with sales increases in each of our markets, driven by growth in residential remodeling and new construction.
The segment's adjusted margin expanded to approximately 10% due to volume, price, mix and productivity gains, partially offset by inflation.
Given these factors, we anticipate our second quarter adjusted earnings per share to be $3.57 to $3.
67 excluding any restructuring charges.

Summary:
In the first quarter, we had all-time record sales of almost $2.7 billion, an increase of 17% as reported or 9% on a constant basis with adjusted operating income of $329 million, our highest ever first quarter earnings per share of $3.49.
Giving us an earnings per share as reported of $3.36 or excluding charges, $3.49, which is 110% improvement versus prior year.
At this point, we anticipate some material shortages continuing into the second quarter.
Given these factors, we anticipate our second quarter adjusted earnings per share to be $3.57 to $3.