Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Dec. 29, 2019	Dec. 30, 2018
Revenue	$ 797,623	$ 717,431
Gross profit	109,737	98,684
Selling, general and administrative expenses	(46,435)	(42,973)
Income from operations	63,302	55,711
Interest expense	(3,349)	(2,897)
Income before income tax expense	59,953	52,814
Income tax expense	(12,636)	(10,782)
Net income	47,317	42,032
Net income attributable to noncontrolling interests	(7)	(35)
Net income attributable to Tetra Tech	$ 47,310	$ 41,997
Earnings per share attributable to Tetra Tech:
Basic (in dollars per share)	$ 0.87	$ 0.76
Diluted (in dollars per share)	$ 0.85	$ 0.75
Weighted-average common shares outstanding:
Basic (in shares)	54,560	55,390
Diluted (in shares)	55,438	56,366
Subcontractor costs
Cost of revenue	$ (183,600)	$ (164,067)
Other costs of revenue
Cost of revenue	$ (504,286)	$ (454,680)