Cover - USD ($)	10 Months Ended
	Dec. 31, 2021	Apr. 07, 2022	Jun. 30, 2021
Document Type	10-K
Amendment Flag	false
Document Annual Report	true
Document Transition Report	false
Document Period End Date	Dec. 31, 2021
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2021
Current Fiscal Year End Date	--12-31
Entity File Number	001-40706
Entity Registrant Name	Blue Whale Acquisition Corp I
Entity Central Index Key	0001854863
Entity Tax Identification Number	98-1590107
Entity Incorporation, State or Country Code	E9
Entity Address, Address Line One	PO Box 1093
Entity Address, Address Line Two	Boundary Hall
Entity Address, Address Line Three	Cricket Square
Entity Address, City or Town	Grand Cayman
Entity Address, Country	KY
Entity Address, Postal Zip Code	KY1-1102
City Area Code	(345)
Local Phone Number	949-8066
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Elected Not To Use the Extended Transition Period	false
Entity Shell Company	true
Entity Public Float			$ 0
ICFR Auditor Attestation Flag	false
Auditor Name	Marcum LLP
Auditor Location	Chicago, IL
Auditor Firm ID	688
Units Each Consisting Of One Class Ordinary Share And Onefourth Of One Redeemable Warrant [Member]
Title of 12(b) Security	Units, each consisting of one Class A ordinary share and one-fourth of one redeemable Warrant
Trading Symbol	BWCAU
Security Exchange Name	NASDAQ
Class Ordinary Shares Par Value 0. 0001 Per Share [Member]
Title of 12(b) Security	Class A ordinary shares, par value $0.0001 per share
Trading Symbol	BWC
Security Exchange Name	NASDAQ
Redeemable Warrants, each whole Warrant exercisable for one Class A ordinary share at an exercise price of $11.50
Title of 12(b) Security	Redeemable Warrants, each whole Warrant exercisable for one Class A ordinary share at an exercise price of $11.50
Trading Symbol	BWCAW
Security Exchange Name	NASDAQ
Common Class F [Member]
Entity Common Stock, Shares Outstanding		2,548,979
Common Class G [Member]
Entity Common Stock, Shares Outstanding		5,097,958