Line Perpendicular to a Plane Calculator

Build the normal vector and define the line. Supports three-point planes and vector inputs directly. Export results, verify steps, and reuse your values later.

Enter values

Pick a plane method, then provide the point where the perpendicular line should pass.

Line point
This point anchors the perpendicular line in space.
Required

Example data table

Use this sample to test your setup and exports.

Plane input Point for line Perpendicular line (parametric) Intersection point Distance point→plane
2x + 3y − 4z + 6 = 0 (1, −2, 3) x = 1 + 2t, y = −2 + 3t, z = 3 − 4t (49/29, −28/29, 47/29) 10/√29

Formula used

1) Plane normal vector
  • For Ax + By + Cz + D = 0, the normal is n = (A, B, C).
  • For three points P1, P2, P3, use n = (P2 − P1) × (P3 − P1).
  • For point and in-plane vectors u, v, use n = u × v.
2) Perpendicular line through a point

If the line passes through P0 = (x0, y0, z0), then its direction is the plane normal:

r(t) = P0 + t·n
x = x0 + A t, y = y0 + B t, z = z0 + C t
3) Intersection and distance
  • Intersection parameter: t = −(A x0 + B y0 + C z0 + D) / (A² + B² + C²)
  • Distance from point to plane: d = |A x0 + B y0 + C z0 + D| / √(A² + B² + C²)

How to use this calculator

  1. Select a plane method that matches your data.
  2. Enter plane values with consistent coordinate units.
  3. Enter the point where the perpendicular line passes.
  4. Press Calculate to view line equations and checks.
  5. Use CSV or PDF to save your computed output.

Guide and notes

A concise reference for perpendicular lines, intersections, and point-to-plane distance.

1) Meaning

A line is perpendicular to a plane when its direction matches the plane’s normal vector. In 3D design, this gives a “straight out” direction from a surface, not a tilted projection. The calculator builds that direction from your plane input and anchors it at your chosen point. Typical uses include drilling guides, camera rays, and extrusion directions quickly.

2) Plane inputs

You can define the plane by coefficients (A, B, C, D), by three non‑collinear points, or by one plane point plus two in‑plane vectors. These options cover survey grids, CAD vertices, and engineering drawings where the plane is implied by geometry rather than an explicit equation. When you start with points or vectors, the tool computes A, B, C, then D automatically.

3) Line forms

Once the normal n=(A,B,C) is known, the perpendicular line through P0=(x0,y0,z0) is r(t)=P0+t·n. The tool prints parametric and symmetric forms so you can plug into solvers, plot a segment, or verify with substitutions. If a component is zero, the symmetric form is adjusted safely to avoid division by zero.

4) Foot point

The intersection point computed is the orthogonal foot from P0 to the plane along the normal direction. The parameter is t=−(A x0+B y0+C z0+D)/(A²+B²+C²). Substituting t back gives the closest point, useful for offsets, standoff distances, and shortest‑path checks. The intersection also satisfies Ax+By+Cz+D=0 by rounding.

5) Distance output

The shortest distance from the point to the plane is d=|A x0+B y0+C z0+D|/√(A²+B²+C²). The unit normal u=n/||n|| is also returned so you can express direction cosines, compute angles, or normalize for consistent scaling in simulations and toolpaths.

6) Error checks

If A, B, and C are all zero, the plane is invalid and results are blocked. For three‑point input, collinearity is detected using the cross‑product magnitude. For vector input, parallel vectors are rejected. These checks prevent near‑singular normals that can cause huge rounding errors and unstable intersections.

7) Exports and use

Use the example table to test a full run, then download CSV for spreadsheets or PDF for sharing. In field work, keep units consistent (meters with meters, not mixed). In modeling, store the intersection point and distance as constraints. Repeat with multiple points to map clearance across a surface.

FAQs

Can the line pass through a point not on the plane?

Yes. Enter any point P0, and the tool creates the perpendicular line through P0. It also finds the closest intersection point on the plane and the shortest distance between them.

What if I only know three plane points?

Choose the three‑point option and enter P1, P2, and P3. The calculator uses a cross product to build the normal. If the points are collinear, it will warn you and stop.

Why is the direction equal to (A, B, C)?

For a plane Ax+By+Cz+D=0, the gradient vector (A, B, C) is perpendicular to every in‑plane direction. Using it as the line direction guarantees a right angle between the line and plane.

How is the intersection parameter t computed?

The tool substitutes the parametric line into the plane equation and solves for t. The formula is t=−(A x0+B y0+C z0+D)/(A²+B²+C²), which is stable when the normal is nonzero.

What units should I use?

Any consistent unit system works. If your coordinates are in meters, the distance output is in meters. Avoid mixing units across x, y, and z or the distance and intersection will be meaningless.

Can I use the CSV/PDF outputs in reports?

Yes. After a successful calculation, download CSV for spreadsheets or PDF for sharing. Each file includes the plane equation, line forms, intersection point, unit normal, and the point‑to‑plane distance.

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