The images print to be 3 inches by 3 inches, so right around there is good. The most important thing is that your image is a square. If you select a vertical or horizontal image, you’ll need to crop it into a square within our builder, or use a photo-editing app (we recommend canva.com) to add a white border.
In case you’re a bit more technical – we recommend no less than 225x225 pixels and no greater than 900x900 pixels for the best quality print. If you’re familiar with image resolution, anything higher than 300 dpi resolution is too much.