Tutorial

The CSS calc() function

Published on October 8, 2015
author

Alligator.io

The CSS calc() function

Calc() is a CSS function that lets you calculate values right in your CSS. For example:

.pirate {
  position: absolute;
  /* lets have the pirate 20px from the left */
  left: calc(50px - 30px);
}

At first glance you might think Why the heck would I care? I can just set it to 20px. Well things get interesting when you realize that you can mix and match the units:

left: calc(1.5em - 8px);

And things get even more interesting when you mix in percentage values. The following sets to width of the selected element to 80px less than 100%:

width: calc(100% - 80px);

Make sure to use spaces around the operand. For example: v1 + v2, not v1 +v2 or v1+v2.

You can use calc() anywhere where you would use numeric values (e.g.: width, max-height, margin-left, …)

Calc() is very useful for things like vertical centering if you know the height of the element you want to center. You just add a margin-top to the element of 50% of the viewport height minus half the height of the element. Let’s say our element is 100px tall:

.my-element {
  display:block;
  margin-left:auto;
  margin-right:auto;
  /* 50vh = 50% viewport height */
  margin-top: calc( 50vh - 50px );
  width: 200px;
  height: 50px;
}

Browser Support

Can I Use calc? Data on support for the calc feature across the major browsers from caniuse.com.

Thanks for learning with the DigitalOcean Community. Check out our offerings for compute, storage, networking, and managed databases.

Learn more about our products

About the authors
Default avatar
Alligator.io

author

While we believe that this content benefits our community, we have not yet thoroughly reviewed it. If you have any suggestions for improvements, please let us know by clicking the “report an issue“ button at the bottom of the tutorial.

Still looking for an answer?

Ask a questionSearch for more help

Was this helpful?
 
Leave a comment


This textbox defaults to using Markdown to format your answer.

You can type !ref in this text area to quickly search our full set of tutorials, documentation & marketplace offerings and insert the link!

Try DigitalOcean for free

Click below to sign up and get $200 of credit to try our products over 60 days!

Sign up

Join the Tech Talk
Success! Thank you! Please check your email for further details.

Please complete your information!

Featured on Community

Get our biweekly newsletter

Sign up for Infrastructure as a Newsletter.

Hollie's Hub for Good

Working on improving health and education, reducing inequality, and spurring economic growth? We'd like to help.

Become a contributor

Get paid to write technical tutorials and select a tech-focused charity to receive a matching donation.

Welcome to the developer cloud

DigitalOcean makes it simple to launch in the cloud and scale up as you grow — whether you're running one virtual machine or ten thousand.

Learn more