Graph a Linear Equation (y = mx + b)
A linear equation y = mx + b graphs as a straight line with slope m (rise over run) that crosses the y-axis at b; drag the sliders for m and b to see it change.
At a glance
| What it is | Graph linear equations y = mx + b online. Drag sliders for the slope m and y-intercept b and see how the line changes. Free, no sign-up. |
|---|---|
| Type | Interactive guide with a calculator |
| Level | High school and college |
| Price | Free, with no account or sign-up |
| Works offline | Yes, after the first visit; installs as an app |
| Made by | Aalok (aalok.builds@gmail.com) |
| Last updated | 1 November 2026 |
Key facts
| Slope-intercept form | y = mx + b |
|---|---|
| Slope | m = rise ÷ run = (y₂ − y₁) ÷ (x₂ − x₁) |
| y-intercept | (0, b) |
| x-intercept | (−b ÷ m, 0) when m ≠ 0 |
| Domain and range | All real numbers (range is just b when m = 0) |
What do the slope and the intercept do?
The slope m says how steep the line is: for every 1 step right, the line goes up m steps. A positive slope rises from left to right, a negative slope falls, and m = 0 gives a horizontal line.
The y-intercept b moves the whole line up or down without changing its steepness.
How do you find parallel and perpendicular lines?
Parallel lines have the same slope, such as y = 2x + 1 and y = 2x − 3. Perpendicular lines have slopes that multiply to −1, such as y = 2x and y = −½x.
How to use it in Plotline
- The graph of y = mx + b with sliders for m and b is already loaded above. Edit the equation in the list to change it.
- Drag the graph to move around, scroll or pinch to zoom, and tap the crosshair to reset the view.
- Hover over or tap the curve to read the coordinates of any point.
- Press Enter to add another equation and compare graphs in different colors.
Frequently asked questions
How do I graph y = 2x + 1?
Type y = 2x + 1 into Plotline. The line crosses the y-axis at 1 and rises 2 units for every 1 unit to the right.
How do I find the slope from two points?
Divide the change in y by the change in x: m = (y₂ − y₁) ÷ (x₂ − x₁). For (1, 3) and (3, 7) the slope is (7 − 3) ÷ (3 − 1) = 2.
Is it free?
Yes. The graphing calculator is free with no account and no sign-up: plot as many equations as you like, use sliders, save graphs in your browser and share them by link. It installs as an app and keeps working offline.
Learn more
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Plotline is an independent project and is not affiliated with Desmos, Texas Instruments or Casio.