Confidence level of effort estimates in JIRA

What (%) n开发者_开发问答umber shall I put under confidence level estimate in JIRA when accepting requirements?

I understand that theoretically, 100% is ideal, but does 80% seem good enough given that I am comfortable with my estimates?

The confidence level really should vary on a issue by issue basis. There are several factors that can increase my confidence level on a task, which can include:

• The vagueness of the requirement being built.
• My familiarity with the technology/stack/libraries being worked on.
• My familiarity with the codebase(s)
• Whether the item has been done before.
• Am I introducing/using any new libraries/frameworks that I am not familiar with.
• The existence of automated testing on the existing modules/projects.
• The complexity of the feature/issue being added.