8:5 aspect ratio. See the table below for proper colours.

David Benbennick made this flag, based on a PNG flag uploaded by User:Rfl. The colours were initially the same as Image:Herb Polski.png. They were then modified by Halibutt in accordance with the official act on Warsaw's symbols [1] archive copy at the Wayback Machine. The flag has been updated again according to the before mentioned source as it states different values now.

This image is ineligible for copyright. But just in case:

This image is in the public domain according to Article 4, case 2 of the Polish Copyright Law Act of February 4, 1994 (Dz. U. z 2022 r. poz. 2509 with later changes) "normative acts and drafts thereof as well as official documents, materials, signs and symbols are not subject to copyrights". Hence it is assumed that this image has been released into public domain. However in some instances the use of this image in Poland might be regulated by other laws.

Ja, nositelj autorskog prava za ovo djelo, prepuštam ovo djelo u javno vlasništvo. Ovo prepuštanje vrijedi za cijeli svijet. U nekim državama to nije pravno moguće; ako je tako: Dajem svima prava da koriste ovo djelo za bilo koju svrhu, bez ikakvih uvjeta, osim ako takvi uvjeti nisu propisani zakonom.