Perpendicular Line Calculator
Find the equation of the line perpendicular to a line through a point.
What is Perpendicular Line?
Perpendicular lines meet at a right angle, and in coordinate terms that means their slopes multiply to −1 — each is the negative reciprocal of the other. A slope of 2 pairs with −1/2, and a slope of 1 pairs with −1.
How it works
The engine flips the reference slope and negates it (m₂ = −1 ÷ m₁), then finds the intercept through your point. The two degenerate orientations are handled as geometry rather than as division by zero: a horizontal reference makes the perpendicular vertical, and a vertical reference makes it horizontal. Both slopes are shown so the −1 product can be checked by hand.
- Enter your input. Type or paste your input into the field above — the tool responds instantly.
- Review the result. Output updates live as you type. Everything runs entirely in your browser.
- Copy or download. Use the Copy button to grab the result, or Download to save it as a file.
Examples
Realistic sample
Type or paste any realistic input — the tool computes the result locally and instantly.
Common mistakes
Expecting a server round-trip
Nothing is uploaded — every tool in this category runs entirely in your browser.