Calculate the derivative of your curve. The derivative is dx divided by dy.
Calculate the second derivative, d squared times y divided by dx, using the result of the first derivative.
Square the result of the first derivative, dy divided by dx, and place that answer into the numerator of the radius of curvature formula.
Input the result of the second derivative, d squared times y divided by dx, into the denominator of the radius of curvature equation.
Solve the equation for a location on your curve. Use a calculator to increase the accuracy and speed of your calculations.