Measuring 21x29cm, 8.27x11.69" is a common size for photo prints, art work and posters. The standard way to measure a print is by measuring width by height.
To get the best print result for 8.27x11.69", you'll need at least 595 x 841px and ideally 2481 x 3507px.
If you are looking for a frame with a mat for an 8.27x11.69" photo, choose the 12x15" (30x38cm) frame. The mat will have an 8.27x11.69" (21x29cm) opening.
