Viewport units in CSS - Cheat Sheet & Quick Revision

Recall & Review

beginner

What are viewport units in CSS?

Viewport units are CSS units that represent a percentage of the browser's visible area. They help make designs responsive by sizing elements relative to the screen size.

beginner

What does 1vw represent?

1vw means 1% of the viewport's width. For example, if the browser width is 1000px, 1vw equals 10px.

beginner

Name the four main viewport units in CSS.

• vw: 1% of viewport width
• vh: 1% of viewport height
• vmin: 1% of smaller viewport dimension (width or height)
• vmax: 1% of larger viewport dimension (width or height)

beginner

Why use viewport units instead of fixed pixels?

Viewport units let elements resize automatically with the browser window. This makes your page look good on phones, tablets, and desktops without extra code.

intermediate

How does vmin behave when viewport width is 800px and height is 600px?

vmin uses the smaller viewport dimension. Here, height is smaller (600px), so 1vmin equals 6px (1% of 600px).

Which viewport unit represents 1% of the viewport height?

A vh

B vw

C vmin

D vmax

vh stands for viewport height, so 1vh is 1% of the viewport height.

If the viewport width is 1200px, what is the pixel value of 5vw?

A 5px

B 12px

C 60px

D 240px

5vw means 5% of 1200px, which is 0.05 × 1200 = 60px.

Which viewport unit uses the larger dimension of width or height?

A vw

B vmax

C vmin

D vh

vmax uses the larger of the viewport width or height.

Why are viewport units useful in responsive design?

A They fix element sizes in pixels

B They only work on desktop browsers

C They replace media queries completely

D They allow elements to scale with screen size

Viewport units let elements resize automatically as the screen size changes, helping responsiveness.

What does 10vmin mean if viewport width is 900px and height is 700px?

A 70px

B 90px

C 100px

D 10px

vmin uses the smaller dimension (700px), so 10vmin = 10% of 700px = 70px.

Explain what viewport units are and list their four types.

Think about how viewport units relate to screen size percentages.

Describe a situation where using viewport units improves a website's design.

Imagine viewing a website on a phone versus a desktop.

Practice

1. What does the CSS unit 1vw represent?

easy

A. 1% of the viewport's width

B. 1% of the viewport's height

C. 1 pixel

D. 1% of the parent element's width

Solution

1. Step 1: Understand viewport width unit

   The unit vw stands for viewport width, so 1vw equals 1% of the browser window's width.

2. Step 2: Compare with other units

   Unlike vh which is viewport height, vw relates only to width, not height or pixels.

3. Final Answer:

   1% of the viewport's width -> Option A

4. Quick Check:

   1vw = 1% viewport width [OK]

Hint: Remember vw = viewport width percent [OK]

Common Mistakes:

• Confusing vw with vh
• Thinking vw is pixels
• Mixing viewport units with parent size

2. Which of the following is the correct CSS syntax to set an element's height to 50% of the viewport height?

easy

A. height: 50vw;

B. height: 50vmax;

C. height: 50vmin;

D. height: 50vh;

Solution

1. Step 1: Identify viewport height unit

   The unit vh means viewport height, so 50vh means 50% of the viewport height.

2. Step 2: Check other units

   vw is viewport width, vmin is the smaller of width or height, and vmax is the larger. Only vh sets height relative to viewport height directly.

3. Final Answer:

   height: 50vh; -> Option D

4. Quick Check:

   Use vh for viewport height in CSS [OK]

Hint: Use vh for height, vw for width [OK]

Common Mistakes:

• Using vw for height
• Confusing vmin and vmax
• Forgetting semicolon in CSS

3. Given this CSS:

div {
  width: 10vw;
  height: 20vh;
}

If the browser window is 1000px wide and 800px tall, what will be the div's width and height in pixels?

medium

A. Width: 200px, Height: 400px

B. Width: 10px, Height: 20px

C. Width: 100px, Height: 160px

D. Width: 1000px, Height: 800px

Solution

1. Step 1: Calculate width from vw

   10vw means 10% of viewport width. 10% of 1000px = 100px.

2. Step 2: Calculate height from vh

   20vh means 20% of viewport height. 20% of 800px = 160px.

3. Final Answer:

   Width: 100px, Height: 160px -> Option C

4. Quick Check:

   vw and vh convert to % of viewport size [OK]

Hint: Multiply vw/vh % by viewport pixels [OK]

Common Mistakes:

• Mixing width and height values
• Calculating percentages incorrectly
• Confusing vh with vw

4. This CSS code is intended to make a box fill the smaller dimension of the viewport, but it doesn't work as expected:

.box {
  width: 50vmin;
  height: 50vmin;
}

What is the likely problem?

medium

A. The viewport units need a unit like px after vmin

B. The viewport size might be changing, causing unexpected results

C. vmin is not supported by browsers

D. The CSS syntax is correct; problem is elsewhere

Solution

1. Step 1: Understand vmin behavior

   vmin uses the smaller of viewport width or height. If viewport changes size (like resizing window), the box size changes too.

2. Step 2: Identify dynamic viewport effect

   Because viewport size can change, the box size changes dynamically, which may look like it doesn't work as expected.

3. Final Answer:

   The viewport size might be changing, causing unexpected results -> Option B

4. Quick Check:

   vmin depends on viewport size changes [OK]

Hint: Remember viewport units react to window resizing [OK]

Common Mistakes:

• Thinking vmin needs px unit
• Assuming viewport units are fixed
• Believing vmin is unsupported

5. You want a square element that always fits inside the viewport without scrolling, using viewport units. Which CSS rule ensures the square's size adapts to the smaller viewport dimension?

hard

A. width: 100vmin; height: 100vmin;

B. width: 100vw; height: 100vh;

C. width: 100vmax; height: 100vmax;

D. width: 100%; height: 100%;

Solution

1. Step 1: Understand vmin and vmax

   vmin is the smaller of viewport width or height, vmax is the larger.

2. Step 2: Choose unit for fitting inside viewport

   To fit inside viewport without scrolling, use vmin so the square fits the smaller dimension.

3. Step 3: Confirm width and height match

   Setting both width and height to 100vmin creates a square that fits inside viewport.

4. Final Answer:

   width: 100vmin; height: 100vmin; -> Option A

5. Quick Check:

   Use vmin for square fitting smaller viewport side [OK]

Hint: Use vmin for size based on smaller viewport side [OK]

Common Mistakes:

• Using vmax causes overflow
• Using 100% depends on parent size
• Confusing vw/vh with vmin/vmax