Document and Entity Information	3 Months Ended
	Mar. 31, 2024 shares
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2024
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q1
Trading Symbol	CPTP
Entity Registrant Name	CAPITAL PROPERTIES, INC.
Entity Central Index Key	0000202947
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Shell Company	false
Entity Emerging Growth Company	false
Entity Current Reporting Status	Yes
Entity File Number	001-08499
Entity Tax Identification Number	05-0386287
Entity Address, Address Line One	5 Steeple Street, Unit 303
Entity Address, City or Town	Providence
Entity Address, State or Province	RI
Entity Address, Postal Zip Code	02903
City Area Code	401
Local Phone Number	435-7171
Entity Interactive Data Current	Yes
Title of 12(g) Security	Class A Common Stock, $.01 par value
Document Quarterly Report	true
Document Transition Report	false
Entity Common Stock, Shares Outstanding	6,599,912
Entity Incorporation, State or Country Code	RI