Line Height Calculator
Calculate optimal line-height for any font size and font family. Adjust the ratio with precision controls and see the result in px, unitless, percentage, and em with a live text preview.
Unitless
1.50
Pixels
24.0px
Percentage
150%
EM
1.50em
Recommended range for body text: 1.40 - 1.80 (optimal: 1.50)
The quick brown fox jumps over the lazy dog. Line height determines the vertical space between lines of text, making content more readable and accessible.
Adjust the line height slider above to see how the spacing between these lines changes in real time.
font-size: 16px; line-height: 1.5;
Why Use Our Line Height Calculator?
Precise Line Height Calculation
Get exact line-height values in px, unitless, percentage, and em formats from any font size. Our calculator uses standard typographic formulas to ensure your vertical rhythm is mathematically sound and visually consistent across your entire design.
Real-Time Live Preview
See the effect of every adjustment instantly with a live text preview rendered in your chosen font family and size. Type your own sample text to preview exactly how your content will look with the calculated line-height applied.
Smart Recommendations by Font Size
Our tool provides tailored line-height recommendations based on font size - tighter ratios for headings and larger text, more generous spacing for body copy. Follow the suggested range for optimal readability and professional typography.
100% Private & Free
All calculations happen locally in your browser. Your text never leaves your device. No signup, no uploads, no hidden limits - just fast, accurate line-height calculations you can trust for any project.
Common Use Cases for Line Height Calculator
Web Design & Development
Set precise line-height values in your CSS to establish consistent vertical rhythm across your entire website. Use the unitless value for maximum responsiveness and maintainability in your stylesheets.
Content & Blog Layouts
Optimize readability for long-form content by calculating the ideal line-height for your body text. A well-chosen line-height between 1.4 and 1.8 significantly improves reading comprehension and reduces eye strain.
Responsive Typography
When using fluid typography with clamp() or viewport units, use our calculator to determine the correct line-height at every breakpoint. Ensure your text remains readable across all screen sizes and devices.
Design System Tokens
Generate consistent line-height tokens for your design system. Define a scale of line-height values - tight, normal, relaxed, spacious - and use the CSS output directly in your component library or Tailwind configuration.
Accessibility Compliance
WCAG 2.1 recommends a line-height of at least 1.5 for body text. Use our calculator to ensure your typography meets accessibility standards while maintaining visual harmony and design intent.
UI/UX Design Prototyping
Quickly experiment with different line-height values during the design phase. Preview how your typography will render before writing any code, ensuring pixel-perfect alignment with your design mockups.
Understanding Line Height in Typography
What Is Line Height (Leading)?
Line height, traditionally called leading in print typography (from the thin strips of lead placed between lines of metal type), is the vertical distance between the baselines of consecutive lines of text. In CSS, line-height controls the amount of space above and below each line of text, making it one of the most important properties for readability and vertical rhythm. A well-chosen line height transforms dense, uncomfortable text into a smooth, inviting reading experience.
Unlike font size, which is measured from the highest ascender to the lowest descender, line height defines the full height of each line box, including the font glyphs and the spacing above and below them. The difference between line height and font size is distributed equally above the top of the text and below the bottom, creating consistent inter-line spacing.
How Our Line Height Calculator Works
Our calculator uses a straightforward formula: line-height (px) = font-size (px) × ratio. When you adjust the font size or the line height ratio slider, the tool instantly recalculates all four output formats - unitless, pixel, percentage, and em values - showing the relationship between each format clearly.
- Enter your font size - Choose from common presets (8px to 72px) or use the slider for precise control. The font size determines the base measurement for all line height calculations.
- Select a font family - Pick from popular web fonts. Different fonts have different x-heights and ascender/descender ratios, which affect how line height visually appears even at the same numeric value.
- Adjust the line height ratio - Use the slider or click a preset (Tight, Normal, Relaxed, etc.). The tool shows all four output formats simultaneously and updates the live preview in real time.
Line Height Values: What Gets Calculated
- Unitless (recommended): The ratio of line height to font size (e.g. 1.5). This is the best practice for CSS because it inherits cleanly from parent elements and scales proportionally with any font size change. Always prefer unitless line-height in your stylesheets.
- Pixel (px): The absolute line height in pixels (e.g. 24px for 16px text at 1.5 ratio). Useful when you need precise vertical alignment with fixed-size elements, but avoid for body text as it does not scale with user font preferences.
- Percentage (%): The line height expressed as a percentage of font size (e.g. 150%). Behaves similarly to the unitless value but can produce unexpected inheritance results in nested elements.
- Em:Relative to the element's font size (e.g. 1.5em). Similar to percentage but expressed as a multiplier. Em values compound through inheritance, which can cause spacing issues in deeply nested components.
Privacy, Security & Availability
Your privacy is our priority. The Line Height Calculator processes everything locally in your browser using client-side JavaScript. No data is sent to any server - your text, font choices, and settings never leave your device. The tool is completely free with no signup required, no file size limits, and no hidden restrictions. Use it confidently for personal projects, commercial websites, or client work.
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Frequently Asked Questions About Line Height Calculator
For body text (typically 14-18px font size), a line height between 1.4 and 1.8 (unitless) is recommended for optimal readability. The most common choice is 1.5, which provides enough vertical space for the eye to easily track from the end of one line to the beginning of the next without losing your place. For longer-form content like articles and blog posts, aim for 1.6-1.8 to reduce eye strain during extended reading sessions.
Headings and larger text (24px and above) benefit from tighter line height values between 1.0 and 1.3. Since headings are typically short - often just a single line or a few words - they do not need as much vertical spacing. Using a tighter line height for headings also creates a stronger visual contrast with body text, helping establish a clear typographic hierarchy that guides readers through your content.
A unitless value (like 1.5) is calculated relative to the element's font size and is inherited as a ratio - it is the recommended approach for CSS. A pixel value (like 24px) sets an absolute line height that does not scale with font size changes. A percentage (like 150%) behaves similarly to unitless but can produce unexpected results during inheritance. The unitless value is the most maintainable and accessible option for modern web development.
Yes, line height is a critical accessibility factor. WCAG 2.1 Success Criterion 1.4.12 (Text Spacing) recommends a line height of at least 1.5 for body text to ensure readability for users with cognitive disabilities, dyslexia, or low vision. Adequate line height prevents text from appearing cramped and helps users track lines accurately. Using a unitless line height also respects user font-size adjustments in browser settings.
Different font families have different x-heights, ascender heights, and descender lengths, which affect how line height visually appears. For example, a font with a large x-height (like Verdana) will look more spacious at the same line height ratio as a font with a small x-height (like Times New Roman). Always preview your line height with your actual font family to ensure the visual spacing meets your design goals.
The golden ratio (approximately 1.618) is often cited as an aesthetically pleasing line height for body text. In practice, values between 1.5 and 1.8 work well for most body copy. The "perfect" line height depends on your specific font family, font size, line length (measure), and the reading context. Our calculator helps you experiment with different ratios and see the result instantly.
Yes, the Line Height Calculator is completely free to use with no restrictions. There are no signup requirements, no usage limits, and no hidden fees. All calculations are performed locally in your browser - your text and settings never leave your device. You can use it for any project, including commercial websites, client work, or personal design experiments.