Earnings per Share (Tables)

12 Months Ended

Sep. 29, 2019

Earnings Per Share [Abstract]

Schedule of number of weighted-average shares used to compute basic and diluted EPS

The following table sets forth the number of weighted-average shares used to compute basic and diluted EPS:

	Fiscal Year Ended
	September 29, 2019		September 30, 2018		October 1, 2017
	(in thousands, except per share data)
Net income attributable to Tetra Tech	$	158,668	$	136,883	$	117,874
Weighted-average common shares outstanding – basic	54,986		55,670		56,911
Effect of diluted stock options and unvested restricted stock	950		928		1,002
Weighted-average common stock outstanding – diluted	55,936		56,598		57,913
Earnings per share attributable to Tetra Tech:
Basic	$	2.89	$	2.46	$	2.07
Diluted	$	2.84	$	2.42	$	2.04