Scatter plot maker and correlation calculator
Paste two lists of numbers or import CSV. Explore X and Y pairs, Pearson correlation and an optional least-squares regression line.
Your numbers stay in this browser. No account or upload to the server is needed.
How to use it
- Enter matching X and Y values in the same order, or import a two-column CSV.
- Choose “Draw and calculate”. Examine the points, not just the correlation coefficient.
- Turn the regression line on or off and download data as CSV or the chart as SVG.
Method and worked example
r = Σ[(x−mean X)(y−mean Y)] / √[Σ(x−mean X)² × Σ(y−mean Y)²]. A value between −1 and 1 describes the direction and strength of a linear relationship.
Least-squares line: Y = aX + b, where a = Σ[(x−mean X)(y−mean Y)] / Σ(x−mean X)² and b = mean Y − a × mean X.
Correlation is undefined when either column is constant. Constant X prevents fitting a line predicting Y from X. Outliers can strongly affect the result.
Correlation does not prove causation. A value near zero does not rule out a nonlinear relationship. Lottery history does not predict the next independent draw.
Example: X = 1; 2; 3 and Y = 2; 4; 6. Then r = 1, a = 2 and b = 0, so Y = 2X.