Accurate way of getting estimate SAT score?

So I am taking the SAT on January 23rd and I took the PSAT a couple months ago since it was a requirement for school. Apparently they changed the way they score the PSAT so I got an 1140 out of 1520. I wanted to know how I could see an estimate of my score if I took the actual SAT. So I divided 1140 by 1520 and got 75%. I then divided numbers with the old sat scoring system of 2400 (e.g. “number”/2400) until I got 75%. The number I got was 1800. Is this an accurate representation of my SAT score or did I go wrong somewhere?

I think the more accurate way is to take your percentiles and estimate your SAT scores using these tables:
http://research.collegeboard.org/content/sat-data-tables