CSS math functions allow a property value - such as the height, animation-duration, or font-size of an element - to be written as a mathematical expression.

Without using any math, the built-in CSS units like rem, vw, and % are often flexible enough to style HTML elements to achieve a particular user experience.

However, there are cases where we might feel limited by expressing an element's style using a single value and unit. Consider the following examples:

1. We want to set the height of a content area to be "the height of the viewport minus the height of a navbar."
2. We want to add the width of two elements together to define the width of a third element.
3. We want to prevent a variable font-size of some text from growing beyond a certain size.

In all of these cases, we need to rely on math to achieve the desired outcomes. One solution could be to rely on mathematical functions defined by JavaScript, and dynamically set element styles based on results calculated by our scripts.

In many instances, including in the examples above, we can instead utilize math functions built directly into CSS. This solution is often simpler to implement and faster for the browser to execute than using JavaScript.

In total, developers can use a combination of nearly two dozen CSS math functions in their stylesheets. In this guide, we'll exemplify four of the more commonly-used, and introduce those more advanced.

calc(): Basic math operations

In the first two of our three examples above, we want to set the style of an element according to the result of an addition or subtraction operation. This is exactly one of the use cases for calc().

The calc() function lets you specify CSS property values using addition, subtraction, multiplication, and division. It is often used to combine two CSS values that have different units, such as % and px.

The calc() math function takes a mathematical expression as a parameter and returns the result of that expression, e.g.:

property: calc(expression);

calc() Example

Click on the play icon below to see the calc() example in the code playground and try it for yourself.

div {
  background-color: black;
  margin: 4px 0;
  width: 100%;
}

div > code {
  display: block;
  background-color: red;
  color: white;
  height: 48px;
}

.calc1 > code {
  /* Output width: `110px` */
  width: calc(10px + 100px);
}

.calc2 > code {
  /* Output width: `10em` */
  width: calc(2em * 5);
}

.calc3 > code {
  /* Output width: Depends on the container's width */
  width: calc(100% - 32px);
}

.calc4 > code {
  --predefined-width: 100%;
  /* Output width: Depends on the container's width */
  width: calc(var(--predefined-width) - calc(16px * 2));
}

min(): Finding the minimum value in a set

There are cases where we don't want the value of a CSS property to exceed a certain number. Say, for example, we want the width of our content container to be the smaller of "the full width of our screen" and "500 pixels." In those cases, we can use the CSS math function min().

The min() math function takes a set of comma-separated values as arguments and returns the smallest of those values, e.g.:

width: min(32px, 50%, 2rem);

This function is often used to compare two CSS values that have different units, such as % and px.

min() Example

Click on the play icon below to see the min() example in the code playground and try it for yourself.

div {
  background-color: black;
  margin: 4px 0;
  width: 100%;
}

div > code {
  display: block;
  background-color: darkblue;
  color: white;
  height: 48px;
}

.min1 > code {
  /* Output width: Depends on the container's width; */
  /* on this page, likely to be `50%` of the container's width */
  width: min(9999px, 50%);
}

.min2 > code {
  /* Output width: Depends on the container's width; */
  /* on this page, likely to be `100%` of the container's width */
  width: min(9999px, 100%);
}

.min3 > code {
  /* Output width: Depends on the container's width; */
  /* on this page, likely to be `120px` of the container's width */
  width: min(120px, 150px, 90%);
}

.min4 > code {
  /* Output width: Depends on the container's width; */
  /* on this page, likely to be `80px` of the container's width */
  width: min(80px, 90%);
}

max(): Finding the maximum value in a set

Similar to min(), sometimes we don't want the value of a CSS property to go below a certain number. For example, we might want the width of our content container to be the larger of "the full width of our screen" and "500 pixels." In those cases, we can use the CSS math function max().

The max() math function takes a set of comma-separated values as arguments and returns the largest of those values, e.g.:

width: max(32px, 50%, 2rem);

This function is often used to compare two CSS values that have different units, such as % and px.

Notice the similarities and differences between the examples for min() and max().

max() Example

Click on the play icon below to see the max() example in the code playground and try it for yourself.

div {
  background-color: black;
  margin: 4px 0;
  width: 100%;
  height: 48px;
}

div > code {
  display: block;
  background-color: darkmagenta;
  color: white;
  height: 48px;
}

.max1 > code {
  /* Output width: Depends on the container's width; */
  /* on this page, likely to be `50%` of the container's width */
  width: max(50px, 50%);
}

.max2 > code {
  /* Output width: Depends on the container's width; */
  /* on this page, likely to be `100%` of the container's width */
  width: max(50px, 100%);
}

.max3 > code {
  /* Output width: Depends on the container's width; */
  /* on this page, likely to be `90%` of the container's width */
  width: max(20px, 50px, 90%);
}

.max4 > code {
  /* Output width: Depends on the container's width; */
  /* on this page, likely to be `80%` of the container's width */
  width: max(80px, 80%);
}

clamp(): Constraining a value between two values

We can combine the functions of min() and max() by using clamp(). The clamp() math function takes a minimum value, the value to be clamped, and the maximum value as arguments, e.g.:

/* clamped value: 50%, minimum: 100px, maximum: 300px */
width: clamp(100px, 50%, 300px);

• If the value to be clamped is less than the passed minimum value, the function will return the minimum value.
• If the value to be clamped is greater than the passed maximum value, the function will return the maximum value.
• If the value to be clamped is between the passed minimum and maximum values, the function will return the original value to be clamped.

This function is often used to compare two CSS values that have different units, such as % and px.

clamp() Example

Click on the play icon below to see the clamp() example in the code playground and try it for yourself.

div {
  background-color: black;
  margin: 4px 0;
  width: 100%;
  height: 48px;
}

div > code {
  display: block;
  background-color: darkgreen;
  color: white;
  height: 48px;
}

.clamp1 > code {
  /* Output width: Depends on the container's width; */
  /* on this page, likely to be `20%` of the container's width */
  width: clamp(20%, 1px, 80%);
}

.clamp2 > code {
  /* Output width: Depends on the container's width; */
  /* on this page, likely to be `90%` of the container's width */
  width: clamp(10%, 9999px, 90%);
}

.clamp3 > code {
  /* Output width: `125px` */
  width: clamp(125px, 1px, 250px);
}

.clamp4 > code {
  /* Output width: `150px` */
  width: clamp(25px, 9999px, 150px);
}

Advanced CSS Math Functions

When laying out and styling DOM elements, the four basic math functions calc(), min(), max(), and clamp() are often sufficient. However, for advanced uses like mathematics learning materials, 3D visualizations, or CSS animations, you may consider using:

• Stepped value functions
  • round(): calculates a value given a rounding strategy
  • mod(): calculates the remainder of a division operation with the same sign as the divisor
  • rem(): calculates the remainder of a division operation with the same sign as the dividend
• Trigonometric functions
  • sin(): calculates the trigonometric sine of a number
  • cos(): calculates the trigonometric cosine of a number
  • tan(): calculates the trigonometric tangent of a number
  • asin(): calculates the trigonometric inverse sine of a number
  • acos(): calculates the trigonometric inverse cosine of a number
  • atan(): calculates the trigonometric inverse tangent of a number
  • atan2(): calculates the trigonometric inverse tangent given two numbers
• Exponential functions
  • pow(): calculates a number raised to the power of another number
  • sqrt(): calculates the square root of a number
  • hypot(): calculates the square root of the sum of the squares of the given numbers
  • log(): calculates the logarithm of a number (with e as the default base)
  • exp(): calculates e of another number
• Sign functions
  • abs(): calculates the absolute value of a number
  • sign(): calculates the sign (positive, negative, or zero) of a number

Final thoughts

• You can use CSS math functions to create responsive user interfaces without writing any JavaScript code.
• CSS math functions can sometimes be used instead of CSS media queries to define layout breakpoints.
• In 2023, members of the Interop Project selected "CSS Math Functions" as a focus area of improvement. This means that browser vendors are working together to ensure that CSS math functions perform the same across browsers and devices.