Parabola Vertex Foci Directrix Calculator

Solve parabola geometry from common equation forms. Review focus, directrix, axis, vertex, and latus rectum. Export clean results for records, sharing, or study now.

Calculator Input

Formula Used

For a vertical parabola, the standard quadratic form is y = ax² + bx + c. The vertex is h = -b / 2a, and k = ah² + bh + c. The focal distance is p = 1 / 4a. The focus is (h, k + p). The directrix is y = k - p.

For a horizontal parabola, the form is x = ay² + by + c. The vertex is found with k = -b / 2a. Then h is calculated by substituting k into the equation. The focus is (h + p, k), and the directrix is x = h - p.

The latus rectum length is |4p|. Its endpoints pass through the focus and remain perpendicular to the axis of symmetry.

How to Use This Calculator

  1. Select the equation type that matches your parabola.
  2. Enter a, b, and c for quadratic forms.
  3. Enter h, k, and p for vertex forms.
  4. Choose the required decimal precision.
  5. Press Calculate to show the result below the header.
  6. Use CSV or PDF buttons to save your report.

Example Data Table

Equation Type Input Vertex Focus Directrix
y = ax² + bx + c a = 1, b = -4, c = 3 (2, -1) (2, -0.75) y = -1.25
(x - h)² = 4p(y - k) h = 3, k = 2, p = 4 (3, 2) (3, 6) y = -2
(y - k)² = 4p(x - h) h = -1, k = 5, p = 2 (-1, 5) (1, 5) x = -3

Parabola Geometry Guide

A parabola is a curved path formed by equal distances. Every point on it stays the same distance from a fixed focus and a fixed directrix. This property makes the curve useful in geometry, physics, design, and many practical models. The calculator helps convert common equation forms into clear geometric features.

Why the Vertex Matters

The vertex is the turning point of the parabola. It is the lowest point when the curve opens upward. It is the highest point when the curve opens downward. For horizontal parabolas, it is the leftmost or rightmost point. Knowing the vertex gives the center reference for the complete curve.

Focus and Directrix

The focus is a point inside the open side of the parabola. The directrix is a line outside the opposite side. Their spacing controls how wide or narrow the curve becomes. A small absolute p value creates a narrow curve. A large absolute p value creates a wider curve.

Equation Forms

The vertical quadratic form uses y = ax² + bx + c. It is common in algebra problems. The horizontal form uses x = ay² + by + c. Vertex forms are often easier for geometry. They show h, k, and p directly. This makes focus, directrix, axis, and latus rectum faster to identify.

Advanced Uses

This tool supports classroom checking, worksheet creation, graph preparation, and report writing. It also helps compare equation forms. You can inspect the opening direction, focal width, converted equation, and latus rectum endpoints. The export options make it easier to save results for study notes, engineering drafts, or teaching material.

Accuracy Notes

Use enough decimal places when values include fractions or long decimals. Rounding changes the displayed result, not the underlying method. If a is zero in quadratic form, the equation is not a parabola. If p is zero in vertex form, the focus and directrix collapse, so the curve is invalid.

FAQs

What does this calculator find?

It finds the vertex, focus, directrix, axis of symmetry, opening direction, focal width, canonical form, and latus rectum endpoints for supported parabola forms.

Can it handle vertical parabolas?

Yes. Use y = ax² + bx + c or the vertex form (x - h)² = 4p(y - k) for vertical parabolas.

Can it handle horizontal parabolas?

Yes. Use x = ay² + by + c or the vertex form (y - k)² = 4p(x - h) for horizontal parabolas.

What is p in a parabola?

The p value is the directed distance from the vertex to the focus. It also controls the directrix location and focal width.

Why can a not be zero?

If a is zero, the quadratic term disappears. The equation becomes linear, so it no longer represents a parabola.

What is the directrix?

The directrix is a fixed line used to define the parabola. Every point on the curve is equally distant from the focus and directrix.

What is the latus rectum?

The latus rectum is a chord through the focus. It is perpendicular to the axis of symmetry, and its length equals |4p|.

Can I export the result?

Yes. After calculation, you can download the result as a CSV file or a PDF report using the provided buttons.

Related Calculators

Paver Sand Bedding Calculator (depth-based)Paver Edge Restraint Length & Cost CalculatorPaver Sealer Quantity & Cost CalculatorExcavation Hauling Loads Calculator (truck loads)Soil Disposal Fee CalculatorSite Leveling Cost CalculatorCompaction Passes Time & Cost CalculatorPlate Compactor Rental Cost CalculatorGravel Volume Calculator (yards/tons)Gravel Weight Calculator (by material type)

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.