Font Size Calculator

Calculate perfect font sizes for any screen or print layout. Convert between pixels, points, ems, and rems with precision for responsive design.

Calculate and convert font sizes between pixels, points, ems, and rems for responsive design.

Base Size (px):

Screen Width (px):

Unit Reference

px: Absolute pixels

pt: Points (1pt = 1/72 inch)

em: Relative to parent font size

rem: Relative to root font size

%: Percentage of parent

vw: Viewport width percentage

How the Font Size Calculator Works

Enter a base font size in pixels. The calculator instantly converts to all common units: points, ems, rems, percentages, and viewport units.

Set your screen width for accurate viewport unit calculations. Results update as you type. No need to manually calculate conversions.

Copy the complete CSS snippet with all unit options. Use the unit reference to understand when each unit is appropriate. All calculations happen locally in your browser.

When You'd Actually Use This

Responsive web design

Convert between px, em, rem for responsive typography. Ensure consistent sizing across breakpoints. Mobile-friendly fonts.

Print stylesheet creation

Web pixels don't translate to print. Convert to points for print CSS. Accurate printed output.

Accessibility compliance

Use relative units for user scaling. Convert fixed px to em or rem. Meet WCAG requirements.

Working with designers

Designers think in pixels. Developers need flexible units. Bridge the communication gap with conversions.

Learning CSS units

Understand how units relate. See that 16px = 1rem = 100%. Build intuition for CSS typography.

Creating type scales

Calculate harmonious font sizes. Convert base size to heading sizes. Consistent typographic hierarchy.

What to Know Before Using

16px is browser default.Most browsers default to 16px. This makes 1rem = 16px. Base your calculations on this standard.

Ems compound in nested elements.Child elements multiply parent's em value. Can cause unexpected sizes. Rems avoid this issue.

Rems are root-relative.Always relative to html font-size. Predictable sizing. Preferred for accessible, scalable typography.

Points are for print.1pt = 1/72 inch. Use for print stylesheets. Not recommended for screen display.

Pro tip: For modern web development, use rem for most sizing. It's accessible, predictable, and works well with browser zoom. Reserve px for borders and shadows.

Common Questions

What's the difference between em and rem?

Em is relative to parent element. Rem is relative to root (html). Rems are more predictable for font sizing.

When should I use viewport units?

VW/VH for responsive headlines. Text that scales with screen. Use carefully - can get too small on mobile.

How do I convert pt to px?

Multiply points by 1.333 for pixels at 96 DPI. 12pt ≈ 16px. This calculator does it automatically.

What about percentage units?

Percent is relative to parent. 100% = parent size. 150% = 1.5x parent. Similar to ems but different syntax.

Should I use fluid typography?

Fluid type (clamp, vw) scales smoothly. Great for headlines. Combine with min/max for accessibility.

How do I set root font size?

Set html { font-size: 100% } for browser default. Or 62.5% to make 1rem = 10px. Choose your preference.

Is this calculator accurate?

Yes, uses standard conversion formulas. Browser defaults assumed. Results match CSS specifications.

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