How to Find the Slope of a Line
Learn how to find slope from two points, a graph, or an equation, with examples, common mistakes, troubleshooting, and FAQs.
Quick Answer
To find slope, use rise over run. From two points, subtract the y-values and divide by the difference in x-values: slope = (y2 - y1) / (x2 - x1).
What You Need
- Two points, graph, or equation
- Subtraction skills
- Fraction simplification
- Graph paper if using a graph
Safety Precautions
- Keep point order consistent in numerator and denominator.
- Do not divide by zero; vertical lines have undefined slope.
- Remember horizontal lines have slope 0.
- Check signs carefully.
Step-by-Step Instructions
- Step 1
Identify two points
Choose two clear points on the line.
- Step 2
Label coordinates
Write them as (x1, y1) and (x2, y2).
- Step 3
Find rise
Subtract y-values: y2 - y1.
- Step 4
Find run
Subtract x-values in the same order: x2 - x1.
- Step 5
Divide rise by run
Write slope as rise over run.
- Step 6
Simplify
Reduce the fraction if possible.
- Step 7
Check direction
A line rising left to right has positive slope; falling has negative slope.
Practical Example
Example: Points (2, 3) and (6, 11) have slope (11 - 3) / (6 - 2) = 8 / 4 = 2.
Common Mistakes
- Switching point order halfway
- Putting run over rise
- Missing negative signs
- Dividing by zero
- Calling vertical slope zero
- Not simplifying
Troubleshooting
Denominator is zero
The line is vertical, so slope is undefined.
Numerator is zero
The line is horizontal, so slope is 0.
Slope sign seems wrong
Check whether the line rises or falls from left to right.
Graph points are unclear
Choose two points where the line crosses grid intersections.
Helpful Internal Links
FAQs
What does slope mean?
Slope describes how steep a line is and whether it rises or falls.
What is rise over run?
Rise is vertical change and run is horizontal change.
What is the slope of a horizontal line?
The slope is 0.
What is the slope of a vertical line?
It is undefined because the run is zero.
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