What does RMSE points about performance of a model in machine learning?

I am working on Decision Tree algorithm and at the end I calculate RMSE value based on actual labels and predicted values (for regression). Now what I am having difficulty in is in understanding the significance of the RMSE value that I get. I know that the lower the RMSE better is the performance of the model but what RMSE value is considered reasonable low or high? Suppose my RMSE value comes as 20 so does that mean the performance of my model is 80% (means 80% of predictions are correct)?

• – Dawny33 Dec 2 '15 at 14:40
• SO, Standard deviation of what? Observed value or Predicted value? – Kaushik Sep 9 '17 at 9:04

Second remember that RMSE is in the same space as your target values. So it is relative to the variance in your target values. The benchmark of random guessing should get you an RMSE = standard_deviation. So lower than this, your model is demonstrating some ability to learn; above that number, you haven't even learned to guess the mean correctly.