Slope Calculator — Find the Slope of a Line

What this calculator does

Whether you're new to math & education numbers or run them every week, the slope calculator gives the same clean result — with a live chart and a copyable summary you can drop into any doc.

The slope of a line measures how steep it is — how much the line rises (or falls) vertically for every unit it moves horizontally. That is the classic "rise over run" idea. Given any two points on a line, (x₁, y₁) and (x₂, y₂), the slope formula m = (y₂ − y₁) / (x₂ − x₁) gives you a single number: positive for a line going uphill left to right, negative for downhill, zero for a flat horizontal line, and undefined when the line is vertical because the run is zero. This calculator finds slope from two points instantly and also returns the rise, the run, the percent grade, the angle of incline, the y-intercept and the complete slope-intercept equation y = mx + b, so you can move straight from coordinates to a usable line equation.

Common mistakes

• Subtracting the coordinates in a different order on top and bottom — always use (y₂ − y₁) over (x₂ − x₁) with the same point first in both.
• Flipping the formula to run over rise; slope is rise over run.
• Reporting slope 0 for a vertical line — a vertical line has an undefined slope, while a horizontal line has slope 0.
• Dropping a negative sign when one coordinate is negative.
• Confusing the slope m with the y-intercept b in y = mx + b.

When to use it

Use it for algebra and geometry homework (finding slope from two points, writing point-slope or slope-intercept equations, checking parallel and perpendicular lines), for calculus prep where slope becomes the derivative, for physics problems where slope is velocity or acceleration on a motion graph, and for real-world grade work such as roof pitch, wheelchair ramp compliance, road gradient and drainage fall.

Pro tips for the Slope Calculator

• Bookmark this page: the URL and inputs are all you need to reproduce the exact result later.
• Save your favorite scenarios by clicking the star icon — they're stored locally, no account needed.
• For big decisions, run best-case, expected, and worst-case scenarios and compare the breakdowns side by side.

Frequently asked questions

›What is the slope formula?

m = (y₂ − y₁) / (x₂ − x₁). Subtract the y-coordinates to get the rise, subtract the x-coordinates in the same order to get the run, then divide.

›What does rise over run mean?

Rise is the vertical change between two points and run is the horizontal change. Slope is rise divided by run, so a slope of 3 means the line goes up 3 units for every 1 unit it moves right.

›How do I find slope from two points?

Label the points (x₁, y₁) and (x₂, y₂), compute y₂ − y₁ and x₂ − x₁, then divide. Entering both points above does this instantly and shows each step.

›Why is the slope of a vertical line undefined?

A vertical line has the same x-value at both points, so the run is 0 and the formula divides by zero. The line is written x = a instead.

›What is the slope of a horizontal line?

Zero. The rise is 0, so m = 0 / run = 0, and the equation is simply y = b.

›What is point-slope form?

y − y₁ = m(x − x₁). It writes a line using one known point and the slope, and rearranges into slope-intercept form y = mx + b.

›How do I find the y-intercept from the slope?

Use b = y₁ − m·x₁ with either point. The calculator shows b and the finished y = mx + b equation in the breakdown.

›What is the slope of parallel and perpendicular lines?

Parallel lines share the same slope. Perpendicular slopes are negative reciprocals: if m = 2, the perpendicular slope is −1/2.

›How do I convert slope to a percent grade or angle?

Percent grade is m × 100. The angle of incline is arctan(m) in degrees. Both are shown in the results.

›Is a negative slope steeper than a positive one?

Steepness depends on the absolute value. A slope of −4 is steeper than +2; the minus sign only means the line falls from left to right.

›Can I embed the Slope Calculator on my site?

Embedding isn't public yet, but you can link directly to this page — the URL is stable and shareable.

›Where does the formula come from?

The formula shown in the "How it works" section is the same one you'll find in standard math & education references — no proprietary tweaks or hidden weightings.