what are the measurements of the diono olympia?

Hi Rebecca
Thank you for your inquiry – to view the Diono Olympia measurements please click the specification button which is located under the product image. The Olympia is more suited for your 3 year old especially if you want to harness for longer. The Diono Rainier is more suited for a younger baby because it comes with the newborn two-piece infant body insert which is why it cost more than the Olympia. We do strongly recommend if you can contact your nearest Baby On The Move store so our child restraint technician can explain in more detail the features and also check it fits your vehicle and you use it correctly every time. Hope that helps.