Sizes and rem
Explanation of rem units and approved rem values in Client-First.
Webflow defaults to px units. If we type "10" into any Designer input and press "Enter", it will set "10px".
Client-First uses rem, which we can select in the unit dropdown.
What is rem?
Rem stands for "root em".
- Rem is a relative unit of measurement based on the root element's font-size.
- The root element is html.
- Rem is relative to the html font size.
- Most sizes applied in Client-First are in rem.
Inheriting browser font size
In Client-First we inherit the html font-size from the browser.
Browsers initially use 16px as their default html font-size.
1rem = 16px conversion is the browser default.
Based on Client-First approved sizes, we can make quick px conversions to rem. For example, Client-First approved rem values are 0.5, 1, 1.5, 2, 2.5, 3, and so on.
Rem and Client-First are a powerful couple for following best accessibility practices with browser font size.
Every 16px is 1rem when the browser's font-size is set to "default" in browser settings.
When we build our Webflow project, we always use 16px as our base value for calculating rem.
Every rem measurement conversion is a multiple of 16.
To convert px value into rem divide this value by 16.
64px / 16px = 4rem
To convert rem value into px multiply this value by 16.
2rem x 16px = 32px
For convenience, we suggest using easily readable rem values like 1, 2, 2.5, 3, 4, 5.
We want to avoid consistent usage of long number values like 8.4375rem. These values are more difficult to remember and will slow us down in our workflow.
Calculations in Webflow Designer
Inside most unit inputs of Webflow Designer, we can calculate rem natively in Webflow.
Inside the width input of Designer, type "100/16rem", press "Enter", and see the rem value calculated.
We can divide any number by 16 to get its rem value inside Webflow Designer.
Browser font size settings
Browsers use 16px as their default html font size — and browsers allow the user to update the default font size. Users can update their preferences and change the font size settings.
Browser font size settings are an essential accessibility topic. When users update their browser font, the website content should adjust with the change. Client-First rem system adapts to the user's browser font size settings.
When we work in other unit measurements, like px and vw, we ignore the user's preferences to update their browser font size settings.
Rem also respects a user's browser zoom controls. When a user zooms in or out on the page, our layout and content in rem will zoom together with the user.
When we use vw or vh units, browser zoom will not work.
vw relies on browser viewport width (or height in the case of vh). Only a change in the browser window will affect sizes set in those units.
Client-First follows best accessibility practices. The decision to work in rem is directly related to this accessibility and UX benefit.
Learn more about accessibility using rem in our Wizardry vs. Client-First comparison article. This is a technical overview of the benefits of rem as an accessible measurement unit.
Recommended px to rem values
Below is a list of all recommended rem values with their converted px measurement.
These Client-First approved values are a recommendation and not a strict requirement.
This list of sizes is interactive. Update values through the sticky navigation menu.
Closest to Client-First values
Client-First suggests working with these values.
There are 3 exceptions to using the above values.
Using 14px for font-size is common and recommended when 16px is too large. 12px font-size is often too small for typography.
14px = 0.875rem
2. 2px spacing
Use 2px for tiny spacing. If a spacing value less than 4px is needed, use 2px.
2px = 0.125rem
3. 1px is 1px
When using 1px, for example as a CSS border, use 1px as the value.
We do not recommend converting 1px values to rem.
Retina devices have different scaling rules than non-retina devices. Using 1px will create exactly 1px line on any device without retina scaling interference.
1px = 1px
Finsweet Extension px to rem migration tool
Finsweet Extension offers a tool to convert projects created in px to rem.
It will convert every value in the project from px to its computed rem value.
Inside the Client-First tab of Finsweet Extension, the "PX to REM Migrator" candy will manage the size unit migration.