Do not use automated appraisal tools, they all just pick random figures, total waste of time. You will see domainers on here who constantly use them but its usually to get an inflated appraisals for a name they regret registering.
Learn the value yourself or put it up on the appraisal section her on NP
The best tool is your mind and experience. If you can't trust that, then use another human option. Automated tools may shed some valuable data occasionally but as the final appraisal is concerned they are incredibly inaccurate.