net debt ( 1 ) 3091.3 2970.7 3222.1 cash conversion cycle ( in days ) ( 2 ) 19 19 21 ( 1 ) defined as total debt minus cash and cash equivalents . ( 2 ) cash conversion cycle is defined as days of sales outstanding in accounts receivable and certain receivables due from vendors plus days of supply in merchandise inventory minus days of purchases outstanding in accounts payable and accounts payable-inventory financing , based on a rolling three-month average. .
table of contents in this form 10-k , we discuss non-gaap income before income taxes , non-gaap net income , non-gaap net income per diluted share , ebitda , adjusted ebitda and adjusted ebitda margin , which are non-gaap financial measures . we believe these measures provide analysts , investors and management with helpful information regarding the underlying operating performance of our business , as they remove the impact of items that management believes are not reflective of underlying operating performance . management uses these measures to evaluate period-over-period performance as management believes they provide a more comparable measure of the underlying business . additionally , adjusted ebitda is a measure in the credit agreement governing our senior secured term loan facility ( 201cterm loan 201d ) , which is used to evaluate our ability to make certain investments , incur additional debt , and make restricted payments , such as dividends and share repurchases , as well as whether we are required to make additional principal prepayments on the term loan beyond the quarterly amortization payments . for further details regarding the term loan , see long-term debt and financing arrangements within management 2019s discussion and analysis of financial condition and results of operations and note 10 ( long-term debt ) to the accompanying consolidated financial statements . for the definitions of non-gaap income before income taxes , non-gaap net income and adjusted ebitda and reconciliations to net income , see 201cresults of operations 201d . the results of certain key business metrics are as follows: .
what was 2016 gross margin percent?
( dollars in millions ) the net sales of years ended december 31 , 2017 is $ 15191.5 ; the net sales of years ended december 31 , 2016 is $ 13981.9 ; the net sales of years ended december 31 , 2015 is $ 12988.7 ; ( dollars in millions ) the gross profit of years ended december 31 , 2017 is 2449.9 ; the gross profit of years ended december 31 , 2016 is 2327.2 ; the gross profit of years ended december 31 , 2015 is 2115.8 ;
( dollars in millions ) years ended december 31 , 2017 years ended december 31 , 2016 years ended december 31 , 2015
net sales $ 15191.5 $ 13981.9 $ 12988.7
gross profit 2449.9 2327.2 2115.8
income from operations 866.1 819.2 742.0
net income 523.0 424.4 403.1
non-gaap net income 605.8 569.0 503.5
adjusted ebitda 1185.6 1117.3 1018.5
average daily sales 59.8 55.0 51.1
net debt ( 1 ) 3091.3 2970.7 3222.1
cash conversion cycle ( in days ) ( 2 ) 19 19 21