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Fluid Font Size Clamp() Generator

Compute a real fluid CSS clamp() value from a min and max size across two viewport widths, with the slope and intersection shown step by step and a live resize preview.

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Result

This page opens the calculator with a general-purpose fluid font-size setup already filled in: 16px at a 320px viewport up to 24px at a 1280px viewport. That is a comfortable body-to-slightly-larger range that scales smoothly from a typical phone screen to a typical desktop window, and it is the setup most people mean when they search for a fluid font-size clamp() in the first place.

The four numbers are open to change: raise the max size for a heading rather than body text, or narrow the viewport range if the design only needs to flex between a tablet and a desktop breakpoint. Whatever you enter, the slope and y-axis intersection are recomputed the same way and shown as explicit arithmetic, not hidden inside the final line.

Below the four inputs, a viewport-width slider drives a live preview so the scaling is visible immediately, and the copy-ready clamp() line is one click away. Switching the output unit between rem and px recalculates every number without touching the min and max size values themselves.

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Accepted Formats & Rules

  • Real fluid-typography math: slope, vw coefficient and y-axis intersection shown explicitly, not just the final clamp() line.
  • Live preview: drag the viewport-width slider to watch sample text resize exactly as it would while a real browser window is resized.
  • Type-scale mode: a base size and a ratio from 1.125 to 1.5 generate six fluid clamp() steps — small, base, h4, h3, h2, h1 — as copy-ready CSS.

Key Benefits

✓ The clamp() line, the slope and intersection numbers, and the live preview all update as you type — no button to press.
✓ A viewport-width slider drives a live preview box, so you see the exact fluid scaling in action between the min and max breakpoints, not just a formula.
✓ A separate type-scale mode turns one base size and ratio into a full 6-step fluid heading scale, ready as a block of CSS custom properties.

Use Cases

  • • Turn a min/max font size and viewport range into a real clamp() line — slope, vw coefficient and intersection included — instead of eyeballing one from a tutorial.
  • • Drag a viewport-width slider to preview a fluid heading or body size resizing exactly as it would while a real browser window is resized, before committing it to a stylesheet.
  • • Generate a full 6-step fluid type scale (small through h1) from one base size and ratio, copied as a ready-to-paste block of CSS custom properties.
  • • Build a fluid clamp() for spacing (margin, padding, gap) instead of font-size — the same slope/intersection formula applies to any CSS property.