Slope-Intercept Form Calculator
Enter two points, a point and a slope, or a line equation. Get y = mx + b, point-slope form, standard form, both intercepts, distance, angle, and a full graph.
What does slope-intercept form tell you?
The equation y = mx + b packs two facts about a straight line into two numbers:
- m — the slope. How steep the line is, and which way it tilts. A positive m rises left-to-right, a negative m falls, and m = 0 is flat.
- b — the y-intercept. Where the line crosses the y-axis, at (0, b).
Slope-intercept form, piece by piece
From two points to y = mx + b
Slope m is the rise over the run between the two points. The intercept b comes from plugging either point into y = mx + b and solving.
Three ways to write the same line
Slope-intercept, point-slope, and standard form describe the same line rearranged. The calculator shows all three — pick whichever your problem uses.
Vertical lines don't fit y = mx + b
When x₁ = x₂ the slope formula divides by zero. The calculator reports the line as x = constant instead of pretending m exists.
Features of this calculator
- Three input modes: two points, one point + slope, or a line equation (y = mx + b or Ax + By = C)
- Computes slope m, y-intercept b, and x-intercept (with a clean note when the line is horizontal)
- For two-point input, also shows distance between the points and the angle of incline in degrees and radians
- Shows the same line in point-slope form and standard (Ax + By = C) form with a proper rational approximation — no huge ugly numbers for slopes like 4/3 or 1/6
- Detects vertical lines (x₁ = x₂) and explains why they can't be written as y = mx + b
- Interactive SVG graph with both intercepts marked in distinct colors
- Full step-by-step working laid out in named sections: Answer, Point-Slope, Slope-Intercept expansion, Y-Intercept, X-Intercept, Graph, Standard Form
Frequently asked questions
+What does a slope of zero mean?
Zero slope means the line is perfectly horizontal — y never changes as x moves. The equation collapses to y = b.
+What does undefined slope mean?
Undefined slope happens when the two points sit on a vertical line (x₁ = x₂). The slope formula divides by zero. Such lines are written x = constant instead of y = mx + b.
+Does it matter which point I call (x₁, y₁)?
No. Swap them and both numerator and denominator of the slope formula change sign, so m is unchanged.
+How do I convert to standard form?
Starting from y = mx + b, move mx to the left to get −mx + y = b, then multiply through by a common factor so A, B, and C are integers and A ≥ 0.