How Line Height Calculator Works

Line-height is the vertical spacing between text baselines. Because designers and developers specify it in different ways, it’s easy to lose track of what the browser will actually render. This calculator converts everything to a single truth: the computed line-height in pixels, then derives equivalent unitless, percent, em, and rem forms.

Step-by-Step

• 1) Enter font size: Provide the font size in pixels for the text you’re styling (for example, 16px body copy or 20px UI labels).
• 2) Enter line-height value: Type your current line-height value (like 1.5, 24, 150, or 1.5).
• 3) Choose the unit: Pick how that value should be interpreted (unitless, px, %, em, or rem).
• 4) Set root size (optional): If you use rem-based scales, set the root font size (often 16px) to convert accurately.
• 5) Snap to a baseline grid (optional): Round the computed line-height to a grid such as 4px or 8px to improve vertical rhythm.
• 6) Copy CSS: Use the generated snippets to apply consistent typography in components, pages, and design systems.

Key Features

Convert between all common formats

Whether your design token uses a unitless ratio (like 1.5), a pixel value (24px), or a percentage (150%), the tool shows equivalent values in every format so you can choose what fits your codebase.

Baseline grid rounding for vertical rhythm

Snapping line-height to a baseline grid helps headings, paragraphs, and UI controls align cleanly. Choose a grid size and rounding mode (nearest, up, or down) to reduce awkward half-pixel spacing and inconsistent component heights.

Copy-ready CSS snippets

Get ready-to-paste CSS for unitless (recommended), pixel-based, or rem-friendly styles. This makes it faster to update typography tokens and ensures everyone on the team uses the same conventions.

Practical guidance for readability

The calculator highlights the computed ratio so you can sanity-check your spacing. For body text, many interfaces land somewhere around 1.4–1.7 depending on font and measure, while headings often use tighter spacing for impact.

Live preview mindset

Because different fonts “feel” taller or tighter at the same numbers, previewing your computed line-height is essential. Use the preview to confirm that the text breathes without looking loose.

Use Cases

• Design system tokens: Convert designer specs into consistent CSS variables for type scales and component libraries.
• Responsive typography: Keep unitless line-height ratios that scale when font sizes change across breakpoints.
• Baseline grid workflows: Align headings, paragraphs, and form fields to a 4px or 8px rhythm for cleaner layouts.
• Legacy CSS cleanup: Replace a mix of px and % values with a single convention without changing the visual output.
• UI component consistency: Ensure buttons, inputs, badges, and nav items use compatible line-height values and don’t “jump” between states.
• Content readability checks: Validate that long-form text has enough vertical spacing for comfortable scanning and reduced fatigue.

In practice, line-height decisions affect everything from reading comfort to component alignment. By converting and rounding values in one place, you can standardize typography quickly and reduce visual inconsistencies across your product.

Optimization Tips

Prefer unitless line-height for scalable UI

A unitless line-height (like 1.5) scales automatically with font-size and avoids surprising inheritance issues. It’s a strong default for design systems, especially when components reuse typography tokens at multiple sizes.

Snap to a grid when layout alignment matters

If your layout uses an 8px spacing system, consider a 4px baseline grid for text. Rounding computed line-height to that grid can make stacked elements look more intentional, particularly in dense dashboards and forms.

Check measure and font metrics

Wide paragraphs often need a little more line-height, while narrow columns can look too loose at the same ratio. Fonts with tall x-heights may also feel tighter, so use the preview and adjust for the specific typeface.

FAQ