v3.26.1
Earnings per Share ("EPS") (Tables)
 6 Months Ended
Mar. 29, 2026
Earnings Per Share [Abstract]  
Summary of number of weighted-average shares used to compute basic and diluted EPS
The following table presents the number of weighted-average shares used to compute basic and diluted EPS (in thousands, except per share data):
 Three Months EndedSix Months Ended
 March 29,
2026		March 30,
2025		March 29,
2026		March 30,
2025
Net income attributable to Tetra Tech$93,623 $5,388 $198,651 $6,135 
Weighted-average common shares outstanding – basic260,144 265,728 260,635 266,819 
Effect of dilutive stock options and unvested restricted stock1,775 1,711 1,848 1,936 
Shares issuable assuming conversion of convertible notes— — — 936 
Weighted-average common shares outstanding – diluted261,919 267,439 262,483 269,691 
Earnings per share attributable to Tetra Tech:    
Basic$0.36 $0.02 $0.76 $0.02 
Diluted$0.36 $0.02 $0.76 $0.02