PX to REM Converter

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

Divide the pixel value by the root font size: 24px ÷ 16px = 1.5rem. 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: Should every pixel value in my design become rem?

Type, spacing and container widths, yes — they should all grow when a reader enlarges their text. Hairline borders and small shadow offsets are the common exceptions: a 1px border scaled to 1.25px just renders soft, with no benefit to anyone. Convert what should scale and leave the rest alone.

Convert pixels to rem units against any root font size, with a conversion table for 16px and 62.5% setups.

Value to convert (px)

Result (rem)

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

px	rem

What It Does

This tool converts pixels (px) to rem 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 rem 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 pixels (px) into a stylesheet that uses rem for accessibility.
You inherited a codebase that mixes units and you need the rem equivalent of an existing px value.
You want to check what a px 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

24

24px is 1.5rem at the 16px browser default.

10

10px is 0.625rem at a 16px root — or exactly 1rem if your CSS uses the html { font-size: 62.5% } trick.

1440

Container widths convert too: 1440px is 90rem, which keeps a max-width scaling with the reader's font size.

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 pixels (px) 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 rem 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 px 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 pixels (px) to rem?

What root font size should I use?

Should I use px or a relative unit?

Is my data sent anywhere?

Should every pixel value in my design become rem?

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