About Vertex Form Calculator
This vertex form calculator rewrites y = ax² + bx + c as y = a(x - h)² + k, so the highest or lowest point of the parabola is visible straight away. It is free, needs no sign-up and runs in your browser, so nothing you enter is uploaded.
The vertex has x coordinate h = -b/(2a), and k is the value of the quadratic at h. The line x = h is the axis of symmetry. If a is positive the parabola opens up and k is the minimum value; if a is negative it opens down and k is the maximum.
The page opens on x² - 6x + 5, whose vertex is (3, -4). The completing-the-square steps are shown as well, since that is how vertex form is usually derived in class.
How to use Vertex Form Calculator
- Choose what to show: Roots, Discriminant, Vertex or Completing the square.
- Enter a, b and c in their boxes, or switch to Equation and type something like 2x^2 - 7x + 3 = 0.
- Read the headline answer. It updates as you type, with no calculate button.
- Open the steps underneath to follow the substitution into the quadratic formula, or the completing-the-square route.
- Use the table for the factored form, vertex form, axis of symmetry and y-intercept, and the graph to see where the parabola crosses the x axis.
Features
- Exact roots: rational, simplified radical or complex, never only a rounded decimal.
- Discriminant with a reading: two real roots, one repeated root or a complex pair.
- Vertex, axis of symmetry, y-intercept and whether the parabola opens up or down.
- Factored form over the rationals when it exists, with the complex factorisation otherwise.
- Completing the square written out, ending in vertex form.
- Quadratic formula steps in KaTeX, with a copy button for the LaTeX.
- Interactive plot with roots and vertex marked, zoom, pan and PNG export.
- Accepts integers, decimals, fractions and a full equation.
Vertex form from standard form
Use the vertex formula, or complete the square. Both give the same h and k.
h = -b / (2a)
k = c - b² / (4a)
y = a(x - h)² + kWorked examples
y = x² - 6x + 5 gives y = (x - 3)² - 4, vertex (3, -4)
h = 6/2 = 3 and k = 5 - 9 = -4. The roots are 1 and 5, symmetric about x = 3.
y = -2x² + 4x + 1 gives y = -2(x - 1)² + 3, vertex (1, 3)
a is negative, so the parabola opens downward and 3 is the maximum value.
Privacy: how it works
- Everything is calculated by code running in your browser tab. The coefficients you enter are not sent to Ulkaa or to any other server, and there is nothing to sign in to.
Tips
- Check an answer by substituting a root back into the equation: the left side should come out as 0.
- If the roots look awkward, look at the discriminant first. A perfect square means rational roots and a clean factorisation.
- The sum of the roots is -b/a and their product is c/a, which is a quick check on any pair of roots.
Frequently asked questions
Is it really free?
Yes. There is no price, no trial and no credit card. Ulkaa Tool does the work with your own device, so there is no server bill to pass on to you.
Do I need an account?
No. There is no sign-up and no login. Open the page and use it. An Ulkaa account is not needed for anything on this tool.
Does it run in my browser?
Yes. Coefficients are processed by code running in your browser tab, on your own device.
Is my data uploaded?
No. Coefficients are never sent to Ulkaa or to anyone else. You can check this yourself by watching the Network tab in your browser developer tools while you use the tool.
How do I convert standard form to vertex form?
Find h = -b/(2a), then k = c - b²/(4a), and write y = a(x - h)² + k. Completing the square gives the same result.
What does the sign of a tell me?
A positive a means the parabola opens upward and the vertex is the lowest point. A negative a means it opens downward and the vertex is the highest point.
More Quadratic Formula Calculator pages
- Quadratic Formula CalculatorEnter a, b and c, or type the equation, and get the roots with every step, the vertex and a graph of the parabola.
- Discriminant CalculatorEnter a, b and c to get the discriminant and what it says about the roots.
- Completing the Square CalculatorEnter a, b and c to see the equation rewritten as a perfect square, step by step.
- Quadratic Equation With Complex RootsSolve a quadratic with no real roots and get the complex pair, with the working.