Parallel Line Calculator

Summary

Find the equation of a line parallel to a given line and passing through a specific point, or check whether two lines are parallel.

How it works

1. Read the slope m from the reference line. Slope-intercept form (y = mx + b) gives m directly; standard form Ax + By = C gives m = -A/B.
2. Keep that same slope — parallel lines always share an identical slope and differ only in their y-intercept.
3. Find the new y-intercept by substituting the target point (x0, y0): b = y0 - m * x0.
4. Write the parallel line as y = mx + b. For a vertical reference line (undefined slope), the parallel line is simply x = x0.

Use cases

• Geometry homework — find a parallel line through a given point.
• Engineering drawing — compute a line offset from a reference line.
• Coordinate geometry — verify whether two road or rail segments are parallel.
• Computer graphics — determine parallel guidelines for layout alignment.

Frequently Asked Questions