Line Height Calculator – Calculate, Convert, and Preview Line Heights
About the Line Height Calculator
The Line Height Calculator converts a font size and line height into every CSS unit at once, pixels, unitless, percentage, em, and rem, so you always know the exact equivalent no matter which unit your codebase uses. Enter your values, pick the input units, and every result updates instantly alongside a live text preview and typography stats.
It’s built for front-end developers and designers who need to translate a design spec’s line height into code, audit an existing stylesheet, or fine-tune readability for a block of body text. If you’re also setting the type scale for a design system, the Golden Ratio Calculator is a useful companion for calculating proportional font size steps that pair well with a given line height.
Once your typography is dialed in, the CSS Text Shadow Generator can add depth to headings without disrupting the line spacing you’ve just calculated, and the CSS Border Radius Generator is handy for finishing the surrounding UI elements in the same session.
Our team verified this calculator against unitless, pixel, percentage, em, and rem line-height inputs, confirming the leading and scale-ratio stats matched manual CSS calculations in every case.
How to Use the Line Height Calculator
- Enter your Font Size and choose its unit: px, em, or rem.
- Enter your Line Height and choose its unit: unitless, px, %, em, or rem.
- Review the Calculated Results grid to see the equivalent value in all five CSS units at once.
- Check the Live Preview to see how the font size and line height actually render on real text.
- Use the Leading and Scale Ratio stats to understand the spacing relationship between font size and line height.
- Click Copy CSS to grab ready-to-paste
font-sizeandline-heightdeclarations, or Clear All to reset.
Example Usage
Input: Font Size = 16px, Line Height = 1.5 (unitless)
Output: 24px, 1.5, 150%, 1.5em, 1.5rem
The Leading stat shows +8px, meaning 8 pixels of extra space are added between the font’s natural height and the rendered line, and the Scale Ratio confirms 1.5, a commonly recommended line height for body text readability.
Frequently Asked Questions
A unitless value like 1.5 scales proportionally with the font size of each element, including nested elements, whereas a fixed px or rem value can create inconsistent spacing when font sizes change across a page.
A ratio between 1.4 and 1.6 is commonly recommended for body text readability, while headings often use a tighter ratio between 1.1 and 1.3 since large text needs less vertical spacing.
Leading is the extra vertical space added between the font size and the actual line height, calculated as line height in pixels minus font size in pixels, and it directly affects how airy or compact a block of text feels.
A percentage line height, like 150%, behaves similarly to unitless once inherited by child elements, but it can produce different results in some inheritance edge cases, which is why unitless values are generally preferred.
Yes, it’s fully browser-based with no signup required, and all calculations happen instantly without submitting your data anywhere.
