Size 6 woman’s On 5 running shoe. My experience with On brand is they run small especially if you have wide feet like me. If you are a true 6 I’d look up sizing on their website to be safe but what I have read is they run tts or they run a half size small. For a wide footed person It’s probably a whole size or half size small. If you’d like to purchase for a big kid this size is equivalent to a big kids size 4.5. Hope that helps. Any questions lmk.