What is 1.125rem in pixels?

At a 16px root it is 18 CSS px. At a 20px root it is 22.5 CSS px. Multiply 1.125 by the root size.

Should I replace all rem values with px?

A numerical conversion is useful for inspection, but replacing units changes how a layout responds to root-size changes. Test the intended behavior before migrating tokens.

Why do browser DevTools and my calculation differ?

Check the computed html font size, whether the source uses rem or em, and whether you are comparing CSS pixels with physical screenshot pixels.

Utill.net

REM to PX Converter — Check Computed Sizes

Convert rem to px with a custom root font size. Check typography and spacing tokens, compare roots, and copy results. Free browser calculator with examples.

This conversion runs only in your browser — nothing is uploaded.

Value

Unit

Root / base font size

Root / base font size16px
Unitrem

em in real CSS follows the parent element's font-size; this tool approximates rem and em with the same root/base value.

When to use this

Check the pixel equivalent of an existing spacing or typography token.
Compare a design screenshot with CSS using a known root size.
Debug changes caused by a reader's larger default font size.

How the result is calculated

px = rem * rootPx. A 1.125rem body size is 18px at a 16px root and 22.5px at a 20px root. Convert using the computed root size, rather than the font size of the component receiving the token.

Open the full tool

Worked examples

Reference values below use the stated root size. The interactive tool above uses your current settings.

Root font size: 16px. Rounded display values; CSS px and pt are reference units, not a measurement of your screen's physical pixels.
Input	Result	What to check
0rem	0.00px	16px root
0.0625rem	1.00px	16px root
0.5rem	8.00px	16px root
0.75rem	12.00px	16px root
1rem	16.00px	16px root
1.125rem	18.00px	16px root
1.5rem	24.00px	16px root
2rem	32.00px	16px root
3rem	48.00px	16px root

Practical pitfalls

Device pixel ratio and browser zoom change physical screen pixels. This result is in CSS pixels and cannot predict a ruler measurement on screen.
A nested component does not change what rem means. If a token is actually in em, the element's font context matters and this root-based result is not equivalent.

References

Last reviewed: 2026-10-11

Task guides with ready-to-use settings

PX to REM Converter — Custom Root Font Size
Divide the pixel value by the root font size: at a 16px root, 24px is 1.5rem. Set the calculator's base to your computed html font size; conversion runs in your browser.
REM to PT Converter — CSS & Print Reference
For CSS reference units, pt = rem * rootPx * 72 / 96. At a 16px root, 1rem is 12pt and 1.5rem is 18pt. Conversion stays in your browser; verify the printed output separately.

Browse all task guides

Frequently asked questions

What is 1.125rem in pixels?: At a 16px root it is 18 CSS px. At a 20px root it is 22.5 CSS px. Multiply 1.125 by the root size.
Should I replace all rem values with px?: A numerical conversion is useful for inspection, but replacing units changes how a layout responds to root-size changes. Test the intended behavior before migrating tokens.
Why do browser DevTools and my calculation differ?: Check the computed html font size, whether the source uses rem or em, and whether you are comparing CSS pixels with physical screenshot pixels.