I don't think we have a totally verified number up to this day. It's definitely several thousands as Ukrainian army actively prevented civilians to leave the city, so significant number died under collapsed buildings.

Overall, according to UN "More than 12,654 civilian men, women, girls, and boys have been killed, and over 29,392 injured since 24 February 2022, as verified by HRMMU."

https://ukraine.un.org/en/289667-civilian-harm-and-human-rig...

https://www.statista.com/statistics/1293409/civilian-deaths-...

With the May of 2025 the total casualties are claimed as 13341:

https://www.statista.com/statistics/1293492/ukraine-war-casu...