Fluid Type Scale Calculator

Generate font size variables for a fluid type scale with CSS clamp.

Overview

Customize everything, grab the output CSS, and drop it into any design system. Share the URL with your team members or use it to document your CSS.

Features

• Fully customizable parameters for everything:
  • Baseline min/max font size, screen width, type scale.
  • The names of the steps in your type scale.
  • The prefix to use for the variable names.
  • The max number of decimal places in the output.
  • Whether to show output in rems or pixels.
  • The resolved pixel value of 1rem.
• Output CSS variables for fluid font sizing.
• Live preview table. Pick a font and enter some sample text to fine-tune the results.
• Link sharing.

Link Sharing

The /calculate route accepts the following query parameters and types. All parameters except boolean flags are required. Booleans that are not specified in the URL are treated as unchecked (false).

Param	Description	Type	Constraints
minFontSize	The minimum font size for the base step	number	> 0 && < maxFontSize
minWidth	The viewport or container width corresponding to the minimum font size	number	> 0 && < maxWidth
minRatio	The type scale ratio for the minimum font size of each step	number	> 0 && < maxRatio
maxFontSize	The maximum font size for the base step	number	> 0 && > minFontSize
maxWidth	The viewport or container width corresponding to the maximum font size	number	> 0 && > minWidth
maxRatio	The type scale ratio for the maximum font size of each step	number	> 0 && > minRatio
steps	A comma-separated list of names for your type scale steps, in ascending order of font size	string	Comma-separated list. Step names must be alphanumeric, with no spaces. No duplicates are allowed.
baseStep	The name of the base step	string	Non-empty string. Must appear in steps.
prefix	The naming convention to use for the output CSS variables	string	Non-empty alphanumeric string.
includeFallbacks	Whether to include fallback variables in the CSS output for browsers that don't support clamp.	on, true, or false
useRems	Whether to use rems for font sizing.	on, true, or false
useContainerWidth	Whether to use container width (cqi) instead of viewport width.	on, true, or false
remValue	The computed pixel value of 1rem. Useful if your app changes the root font size (e.g., with the popular 62.5% font size trick). Note: This parameter has no effect if useRems is omitted.	number	> 0
decimals	The number of decimal places to round the output to.	int	>= 0 && <= 10
previewFont	The font family to render in the preview.	string	Non-empty string. Spaces must be escaped (e.g., Libre+Baskerville). The font must be a valid Google Font. Custom fonts are not supported.
previewText	The text to render in the preview table.	string	Non-empty string. Spaces must be escaped (e.g., This+is+a+sentence).
previewWidth	The width to simulate in the preview table.	number	> 0

Example URL: https://www.fluid-type-scale.com/calculate?minFontSize=15&minWidth=400&minRatio=1.25&maxFontSize=17&maxWidth=1280&maxRatio=1.333&steps=sm%2Cbase%2Cmd%2Clg%2Cxl%2Cxxl%2Cxxxl&baseStep=base&prefix=font-size&decimals=2&useRems=on&remValue=10&previewFont=Libre+Baskerville&previewText=Testing+123&previewWidth=420

Tech Stack

• SvelteKit
• Sass
• TypeScript

Running Locally

1. Clone the repo.
2. Run pnpm install to install dependencies.
3. Run pnpm run dev and visit localhost:5173 to view the app.

Similar Tools

• Utopia.fyi fluid type scale calculator by James Gilyead and Trys Mudford
• Type Scale by Jeremy Church
• Modern fluid typography editor by Adrian Bece
• Fluid Typography by Erik André Jakobsen
• fluidtypography.com by Kip Hughes

Learn More

• Creating a Fluid Type Scale with CSS Clamp, a deep dive I wrote on this topic. The technique covered in the article is the basis for this app.
• Generating font-size CSS Rules and Creating a Fluid Type Scale by Stephanie Eckles
• Consistent, Fluidly Scaling Type and Spacing by Andy Bell