It depends on your marks. Use an atar calculated by entering your raw scores. But that would only give a rough estimate.
ATAR calculators essentially just spit out an output given an input. If you feed it rubbish, it will likewise spit out rubbish.
You should never input your raw scores into the ATAR calculator since they're not scaled, and the difficulty of school assessments can vary by orders of magnitude across different schools. The ATAR calculator is only accurate if you input your scaled HSC scores. The question of how you can approximate your HSC mark is a tricky one. If you have any friends in the grade above you at school, the most accurate method is probably to ask them for their rank and their HSC mark. You can then use that as a reference to give you some indication of what to expect.