What base font size should I use?

The browser default root font size is 16px, which is the most common setting. Some designers use 10px to make rem math easier. Our font size converter supports any base font size - choose from presets or enter a custom value.

How do vw units work for font sizes?

vw (viewport width) units make font size relative to the browser window width: 1vw = 1% of the viewport width. On a 1920px-wide screen, 1vw = 19.2px. VW is often used inside CSS clamp() functions with min and max fallbacks for fluid typography.

What is the formula for converting px to rem?

rem = px ÷ root font size. With the default root of 16px: 16px = 1rem, 24px = 1.5rem, 32px = 2rem. For vw: vw = (px ÷ viewport width) × 100. For pt: pt = px ÷ 1.333. Our font size converter applies all formulas instantly.

Is my data safe when using this font size converter?

Yes. All conversions happen 100% client-side in your browser. Your values are never sent to any server, never stored, and never transmitted anywhere.

Font Size Converter

Convert font sizes between px, em, rem, %, pt, and vw instantly with our free font size converter. Enter any value, choose the input unit, and get live results across all six CSS units with a configurable base font size and viewport width. Includes a live text preview, clickable unit cards for continued conversion, a reference table for common pixel values, and one-click copy for every value. Fully private, 100% free, and no signup required.

Font Size Converter

Convert font sizes between px, em, rem, %, pt, and vw with configurable base font size and viewport width. See live results and a full reference table for common pixel values.

Value to Convert

Base (Root) Font Size

Viewport Width (for vw)

CSS Output

font-size: 16px;

Preview

The quick brown fox jumps over the lazy dog

Preview at 16px -

Common Font Sizes

Reference Table - Common PX Values(root: 16px, viewport: 1920px)

px	rem	em	%	pt	vw
4	0.25	0.25	25%	3	0.2083
8	0.5	0.5	50%	6	0.4167
10	0.625	0.625	62.5%	7.5	0.5208
12	0.75	0.75	75%	9	0.625
14	0.875	0.875	87.5%	10.5	0.7292
16	1	1	100%	12	0.8333
18	1.125	1.125	112.5%	13.5	0.9375
20	1.25	1.25	125%	15	1.0417
24	1.5	1.5	150%	18	1.25
28	1.75	1.75	175%	21	1.4583
32	2	2	200%	24	1.6667
36	2.25	2.25	225%	27	1.875
40	2.5	2.5	250%	30	2.0833
48	3	3	300%	36	2.5
56	3.5	3.5	350%	42	2.9167
64	4	4	400%	48	3.3333
72	4.5	4.5	450%	54	3.75
96	6	6	600%	72	5

Why Use Our Font Size Converter?

Instant Multi-Unit Conversion

The font size converter instantly shows equivalent values across all six units - px, em, rem, %, pt, and vw - as you type. No button to press, no page reload. Each unit card is clickable so you can continue converting from any output unit immediately.

Configurable Base & Viewport

Set the root font size (default 16px) and viewport width (default 1920px) to match your project context. Choose from common presets or enter custom values. All conversions update instantly when you change these settings.

100% Private - No Upload

All font size conversions happen locally in your browser. Your values never leave your device and are never sent to any server - safe for proprietary design systems and client work.

Free & No Limits

Convert unlimited font sizes with no signup, no subscription, and no usage caps. The font size converter is completely free forever with no ads blocking the interface.

Common Use Cases for Font Size Converter

UI & Web Design

UI designers use the font size converter to translate mockup font sizes (typically in px from Figma or Sketch) into responsive rem or em units for development. This ensures designs are implemented accurately while maintaining accessibility and scalability.

CSS Development

Frontend developers use the font size converter to convert design spec pixel values into the CSS unit best suited for each use case - rem for global typography, em for component-scoped sizing, vw for fluid headings, and pt for print stylesheets.

Responsive Typography

Developers building responsive sites use the font size converter to calculate fluid type scales. By converting between px and vw units at different viewport sizes, they can create clamp() functions that scale text smoothly across all screen sizes.

Design System Tokens

Design system maintainers use the font size converter to define consistent type scale tokens. Converting a base set of pixel values into rem, em, and percentage ensures the design system works across all CSS unit contexts.

Accessibility Compliance

Accessibility specialists use the font size converter to verify that font sizes meet WCAG requirements. Understanding the relationship between px and rem helps ensure text respects user font size preferences (WCAG 1.4.4 Resize Text).

Print & PDF Design

Print designers use the font size converter to translate between px (screen) and pt (print) units. This ensures that digital designs can be accurately reproduced in print at the correct physical size.

Understanding CSS Font Size Units

What is a Font Size Converter?

A font size converter translates font size values between different CSS units - px, em, rem, %, pt, and vw. Each unit has different characteristics and use cases. Our tool converts any input value to all six units simultaneously, with configurable base font size and viewport width settings to match your exact project context. All conversions happen instantly in your browser.

Understanding Each CSS Font Unit

px (Pixels): A fixed-size unit equal to one screen pixel. Pixels are absolute and do not scale with user preferences. Best used for borders, shadows, and fine details - not recommended for text in responsive designs due to accessibility concerns.

rem (Root EM): Relative to the root (<html>) element's font size. 1rem = root font size (default 16px). REM is the most predictable relative unit - it scales consistently regardless of nesting depth. Recommended for global typography and spacing in modern CSS architectures.

em: Relative to the parent element's font size. 1em = parent font size. EM units compound with nesting - if a parent has font-size: 2em and the child also has font-size: 2em, the child is 4× the root size. Useful for component-scoped sizing that should scale with its container.

% (Percent): A percentage of the parent element's font size. 100% = parent font size. Percentages behave identically to em units but use a different syntax. Often used for line-height and vertical rhythm in typographic systems.

pt (Points): A physical unit used in print typography. 1pt = 1/72 of an inch. In CSS, pt is typically used for print stylesheets. On screen, 1pt ≈ 1.333px (at 96 DPI). Our converter uses the standard CSS relationship of 1pt = 1.333px.

vw (Viewport Width): A percentage of the viewport width. 1vw = 1% of the viewport width. VW units create fluid typography that scales with the browser window. Often used in combination with clamp() for responsive headings that scale smoothly between min and max sizes.

Why Use Relative Units for Font Sizes?

Using relative units (rem, em, vw) for font sizes is a WCAG accessibility requirement.WCAG 2.1 Success Criterion 1.4.4(Resize Text) requires that text can be resized up to 200% without loss of content or functionality. When you use px for text, it ignores the user's browser font size preference - a user who sets their browser to 20px default will see the same small text as a user with 16px.

REMis the recommended unit for typography in most modern CSS architectures because it respects user preferences, provides consistent sizing across the entire page, and makes global font size adjustments as simple as changing a single value on the <html> element. Our font size converter helps you translate pixel-based design specs into accessible, responsive units.

How to Use This Font Size Converter

Enter a value: Type any positive number in the input field. Select the unit (px, em, rem, %, pt, or vw) from the dropdown menu. The converter instantly shows results in all six units.
Configure base settings: Set your root (base) font size and viewport width to match your project. Quick presets are available, or enter a custom value. Changing these settings updates all conversions in real time.
Review and copy: Each unit card shows the converted value. Click any card to make that unit the new input for continued conversion. Hover over any card and click the copy icon to copy the formatted value. A CSS declaration is also provided for quick copy-paste into your stylesheet.
Use the reference table: The reference table shows common pixel values converted to all units at your configured settings - ideal for quickly looking up standard sizes.

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Frequently Asked Questions About Font Size Converter

A font size converter translates font size values between different CSS units - px, em, rem, %, pt, and vw. Our converter instantly shows equivalent values across all six units simultaneously, with configurable base font size and viewport width settings. This helps designers and developers work with font sizes in the most appropriate unit for each use case without manual calculations.

Simply enter a positive number in the input field, select the input unit from the dropdown, and the converter instantly shows equivalent values across all six units. Click any output card to make that unit the new input for further conversion. Hover over any card to copy the formatted value. You can also configure the base font size and viewport width using the preset dropdowns or custom values.

rem is relative to the root element (<html>) font size - 1rem always equals the root font size, regardless of where the element is nested. em is relative to the parent element's font size and compounds with nesting. For example, a div with font-size: 2em inside a parent with font-size: 2em will have an effective size of 4× the root. Rem is more predictable for global sizing; em is useful for component-scoped sizing.

The browser default root font size is 16px, which is the most common setting for web projects. Some designers use 10px as the root size to make rem math easier (1rem = 10px, so 1.6rem = 16px). Our font size converter supports any base font size - choose from presets or enter a custom value. The choice depends on your team's preferences and design system conventions.

vw (viewport width) units make font size relative to the browser window width: 1vw = 1% of viewport width. On a 1920px-wide screen, 1vw = 19.2px, so 10vw = 192px. VW units create fluid typography that scales with the window, but can make text too small on narrow screens or too large on wide screens. This is why vw is often used inside CSS clamp() functions with min and max fallbacks.

rem = px ÷ root font size. With the default root of 16px: 16px = 1rem, 24px = 1.5rem, 32px = 2rem, 48px = 3rem. For em units, the same formula applies but uses the parent element's font size instead of the root. For vw: vw = (px ÷ viewport width) × 100. For pt: pt = px ÷ 1.333. Our font size converter applies all these formulas instantly.

Yes. All font size conversions happen 100% client-side in your browser using JavaScript. Your values are never sent to any server, never stored, and never transmitted anywhere. The font size converter is completely private and processes everything locally on your device.

Yes. The font size converter is 100% free with no signup required, no premium features, and no usage limits. Convert unlimited font sizes without any restrictions or hidden costs. There are no ads blocking the interface.