Advanced Runge Kutta Calculator

Compute RK2, RK3, and RK4 solutions precisely. Track k-values, exact comparisons, and interval behavior effortlessly. Export clean tables and visualize numerical solution paths instantly.

Calculator Inputs

Use explicit multiplication such as 2*x or x*y. Supported functions include sin, cos, exp, log, sqrt, and powers like x^2.

Example Data Table

This sample uses y' = x + y, x₀ = 0, y₀ = 1, h = 0.2, xₙ = 1, and exact solution 2*exp(x)-x-1.

Method Equation x₀ y₀ h xₙ Approx Final y Exact Final y
RK4 y' = x + y 0 1 0.2 1 3.436502 3.436564

Formula Used

General Problem

Solve the initial value problem y' = f(x, y) with starting condition y(x₀) = y₀.

RK2 (Heun)

k1 = f(x_n, y_n)

k2 = f(x_n + h, y_n + h*k1)

y_(n+1) = y_n + (h/2) * (k1 + k2)

RK3

k1 = f(x_n, y_n)

k2 = f(x_n + h/2, y_n + (h/2)*k1)

k3 = f(x_n + h, y_n - h*k1 + 2*h*k2)

y_(n+1) = y_n + (h/6) * (k1 + 4*k2 + k3)

RK4

k1 = f(x_n, y_n)

k2 = f(x_n + h/2, y_n + (h/2)*k1)

k3 = f(x_n + h/2, y_n + (h/2)*k2)

k4 = f(x_n + h, y_n + h*k3)

y_(n+1) = y_n + (h/6) * (k1 + 2*k2 + 2*k3 + k4)

How to Use This Calculator

  1. Enter the differential equation in the form f(x, y).
  2. Choose RK2, RK3, or RK4 based on the accuracy you need.
  3. Enter the initial point x₀ and initial value y₀.
  4. Provide step size h and the target point xₙ.
  5. Optionally enter an exact solution to compare numerical error.
  6. Press the solve button to show results above the form.
  7. Review the table, summary cards, and Plotly graph.
  8. Download the iteration table in CSV or PDF format.

FAQs

1. What does this calculator solve?

It solves first-order ordinary differential equations written as y' = f(x, y). You provide an initial point and a target x-value, and it computes the numerical solution step by step.

2. Which Runge Kutta method should I choose?

RK2 is faster and simpler, RK3 balances speed and accuracy, and RK4 is usually the preferred general-purpose choice because it offers strong accuracy for many practical problems.

3. Can I compare the result with an exact solution?

Yes. Enter the exact solution in terms of x only. The calculator will display exact values and absolute errors at each computed step.

4. What function syntax should I use?

Use explicit multiplication like 2*x and x*y. Supported forms include sin(x), cos(x), exp(x), log(x), sqrt(x), and powers like x^2.

5. Why does the final step size sometimes change?

If the interval does not divide evenly by the chosen step size, the calculator automatically shortens the last step so the solution ends exactly at the requested target x-value.

6. Does a smaller step size always improve accuracy?

Usually yes, but smaller steps also increase computation time and table length. Very small steps may be unnecessary when RK4 already gives enough precision for your problem.

7. What does the Plotly graph show?

The chart plots the numerical solution against x. If you enter an exact solution, the graph also shows the exact curve so you can visually compare both paths.

8. Can this calculator solve backward intervals?

Yes. If the target x-value is less than the starting x-value, the calculator automatically reverses the step direction and computes the solution backward.

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Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.