Can this be used with the cars seatbelt

Hi Kirsty, thank you for your enquiry, the Child restraint can be used with a seat belt once the child has reached the shoulder markers to comply with the booster mode of the seat. we do not have a measurement of that. We hope this helps. ?For further information on this or any of our other products available, if you follow the link https://www.babyonthemove.co.nz/store-locations/ this will take you to our online store finder. Here you can find contact details for your nearest Baby On The Move Store where one of our team experts will be happy to assist you in your product search and help answer any further questions you may have. We hope this has helped with your query.