REM to PX Converter

Q: How do I convert rem to pixels (px)?

Multiply the rem value by the root font size: 1.5rem × 16px = 24px. The tool does this for you and lets you change the reference size, because that reference is what makes the answer different from one project to the next.

Q: What root font size should I use?

Browsers default to 16px, so 16 is the right starting point unless your stylesheet sets a different size on the html element. If your CSS sets `html { font-size: 62.5% }` — a common trick to make 1rem equal 10px — set the root size to 10 here instead.

Q: Should I use px or a relative unit?

Use relative units (rem, em) for anything that should scale with the reader's font-size preference: type, spacing, and container widths. Pixels are fine for things that genuinely should not scale, such as hairline borders and some shadow offsets. The accessibility rule of thumb is that a user who sets a larger default font size in their browser should see your layout grow with it.

Q: Is my data sent anywhere?

No. The conversion is arithmetic done in your browser — nothing is uploaded, and the page works offline once loaded.

Q: How do I check what my rem values really render at?

Open dev tools and read the computed font size on the html element — that is your true root, whatever your stylesheet intends. Enter it as the base here and every rem in your project converts correctly. It is worth checking rather than assuming, because a stray html { font-size } rule in a vendor stylesheet silently shifts every rem on the page.

Convert rem units to pixels against any root font size, and see what happens when a reader enlarges their default.

Value to convert (rem)

rem

Result (px)

Root / parent font size

Browsers default to 16px. Use 10 if your CSS sets html { font-size: 62.5% }.

About this conversion

The same value at other root sizes

Root size	Result

Common conversions at 16 px

rem	px

What It Does

This tool converts rem to pixels (px) in CSS. The conversion is not a fixed ratio — a rem is relative to the font size of the *root* (html) element — so the tool asks for the size that px is measured against and shows the result for that context. It also prints a full conversion table for the common root sizes, so you can read off the values you need without converting one by one, and tells you when the result lands on a fractional pixel that a browser will round.

When to Use It

You are converting a design handed over in rem into a stylesheet that uses pixels (px) for accessibility.
You inherited a codebase that mixes units and you need the px equivalent of an existing rem value.
You want to check what a rem value becomes when the user changes their browser's default font size.
You are writing a design-token scale and need the same step expressed in both units.

Worked Examples

1.5

1.5rem is 24px at the 16px default.

1

1rem is 16px by default — but 20px for a reader who has set a larger browser font size. That is the point of the unit.

0.5

0.5rem is 8px, the smallest step most spacing scales need.

Features

Instant two-way conversion

Configurable root/parent font size

Full conversion table for common root sizes

Fractional-pixel rounding warning

Copy the value or the whole table

Works offline in your browser

No uploads or tracking

How to Use

1. Enter the rem value you want to convert. 2. Set the root (or parent) font size the value should be measured against — 16px is the browser default. 3. Read the pixels (px) result, or copy the whole conversion table for the sizes you use.

Common Mistakes

Assuming the conversion is fixed. 1rem equals the root element's font size, which the user can change in their browser — the same rem value converts differently depending on that size.
Confusing em with rem. `em` is relative to the *parent* element's font size and therefore compounds when nested; `rem` is always relative to the root element and does not.
Setting a px font size on the root element. That overrides the user's browser font-size preference, which defeats the accessibility reason for using relative units at all.
Rounding too early. Keep the fraction (1.375rem, not 1.4rem) — the browser resolves sub-pixel values fine and the rounding error compounds across a scale.

Frequently Asked Questions

How do I convert rem to pixels (px)?

What root font size should I use?

Should I use px or a relative unit?

Is my data sent anywhere?

How do I check what my rem values really render at?

The conversion runs entirely in your browser. Nothing is uploaded and nothing is stored.