What's a Slope, Anyway?

Spoiler: you already know more about slopes than you think!

Part 1

Slopes Are Everywhere

Have you ever walked up a really steep hill and thought “whoa, my legs are burning”? Or coasted down a gentle ramp on your bike? That feeling of steepness — that's slope!

Steep Hill
Hard to climb!
Gentle Ramp
Easy to roll up
Staircase
Rise & run in steps
Roof Pitch
Rain runs off faster
Ski Run
Green vs black diamond
Ladder Angle
Too steep = dangerous!
Try It — Tilt the Ramp
riserun
Angle: 30°
A moderate slope — picking up speed!
A wheelchair ramp can't be too steep — the law says it can only rise 1 inch for every 12 inches forward. That's a slope of 1/12!
Part 2

Counting the Steepness

OK so slopes are about steepness. But how do we put a number on it? Here's the trick: count how much it goes UP versus how much it goes ACROSS.

Positive
Goes up ↗
Negative
Goes down ↘
Zero
Flat →
Undefined
Straight up ↑

Drag the endpoints on the grid below. Watch the rise and run change!

Drag the Line
Rise: 3Run: 4Slope: 0.75
Think of it this way: if you walk 4 steps forward and go up 3 steps, the slope is 3/4. The bigger that number, the steeper the climb!
Part 3

The Magic Formula

Ready for the formula? You basically already know it. Slope is just rise ÷ run, written fancy:

m = rise ÷ run
m = (y₂ − y₁) / (x₂ − x₁)

Remember tilting that ramp earlier? This formula is just measuring the same thing — how steep something is — but with exact numbers.

Click pairs of points on the graph to draw line segments. Each one gets its own color so you can compare slopes side by side!

Click Points to Compare Slopes

Click anywhere to place your first point. Click and drag existing points to move them.

Slope in Action

Slope = How Fast Things Change

Here's the cool part: slope isn't just about hills. Anytime something changes steadily, you can measure it with slope. Mathematicians call this the “rate of change.”

distancetime
Speed
60 miles / 1 hour · Slope = 60 mph
heightdays
Plant Growth
2 inches / 1 day · Slope = 2 in/day
savings $weeks
Saving Money
$5 / 1 week · Slope = $5/week
total paidmonths
Gym Membership
$15 / 1 month · Slope = $15/month
When you hear “miles per hour” or “dollars per week” — that's a slope! The word “per” is the clue.

Think about a gym membership: you pay $15 every month. After 1 month you've paid $15, after 2 months $30, after 3 months $45. If you graph it, you get a straight line with slope = 15. That steady rate IS the slope!

Part 5

Slope in y = mx + b

You might have seen this equation before: y = mx + b. It looks fancy, but you already know what the pieces mean!

m
The Slope
How steep the line is — the same rise/run from before!
b
The y-intercept
Where the line crosses the y-axis — the starting point!

Drag the sliders to change m and b. Watch how the line moves! Turn on the parallel line to see: same slope = same steepness, just shifted.

Explore y = mx + b
y = 2x + 1
One Move Challenge
Challenge 1 of 2
Drag the sliders to change m and b. Watch how the line moves! Change only m.
Parallel lines have the same slope (same m) but different starting points (different b). They're like railroad tracks — always the same distance apart, never crossing!
Practice

Test Yourself!

Think you've got it? Let's find out. Don't worry — you can try as many times as you want!

Question 1: Which line is steeper?
Question 2: A line goes through (1, 2) and (4, 8). What's the slope?
Question 3: You earn $12 for every hour you babysit. If you graph hours (x) vs earnings (y), what's the slope?
Question 4: A horizontal line has a slope of...
Test Yourself!
Closeness2%
Print Results
Share With Class