If you’ve done the task before, double the estimate. If you’ve never done it before, 10x the estimate. Break tasks down to granularity of 1-8 hours. No more than that. Estimate time != real time because life, meetings, other projects.
I do this for sub-tasks that are relevant to myself only (for example, "create function to do X"), but my minimum estimates are 1/2 a day (in extreme cases like a 1-line fix) or 1 day for anything that goes to a manager.