How do you estimate your deadlines?​

As an Engineering Manager / CTO I have to often set deadlines / estimate project duration , But often I miserabley fail when its an team effort due to my inexperience . I can estimate well if the project is for me and not an team effort . There are always roadblocks and dependencies that makes the projects go past the required timeline .

So wanted to know what are the things to consider while estimating deadlines for a project / How do you estimate at your company ? Do you ask your teammates about estimation about their part or do you have any specific approach for that ?