happytails.ai

PX to REM converter

Open PX to REM converter on Happytails.ai. This view has the same page content and links, with explicit tool capabilities. Read the processing notes before using a tool.

Tool capabilities

{
  "id": "px-to-rem",
  "category": "design-tools",
  "built": true,
  "requirements": "A rem unit is relative to the root element's font size, not the parent element. This calculator does not inspect a webpage or convert em units. Negative values are accepted for properties that support them.",
  "implementation": {
    "fields": [
      {
        "key": "value",
        "label": "Value",
        "value": 24,
        "type": "number",
        "min": -1000000,
        "max": 1000000,
        "step": "any"
      },
      {
        "key": "root",
        "label": "Root font size (px)",
        "value": 16,
        "type": "number",
        "min": 0.01,
        "max": 1000,
        "step": "any"
      },
      {
        "key": "direction",
        "label": "Conversion",
        "value": "Pixels to rem",
        "type": "select",
        "values": [
          "Pixels to rem",
          "Rem to pixels"
        ]
      }
    ],
    "input": false,
    "live": true,
    "presentation": "metrics",
    "note": "rem units use the root element’s font size. The default is 16px, but your CSS can set a different value. This also converts rem back to pixels.",
    "experience": {
      "automatic": true,
      "single": false,
      "inputMaxLength": 1000000,
      "inputMode": "text",
      "label": "Your text",
      "placeholder": "Type or paste your input…",
      "help": "Change the input or settings to update your result. Results update as you type. Up to 1,000,000 characters.",
      "helpParts": [
        "Change the input or settings to update your result.",
        "Results update as you type.",
        "Up to 1,000,000 characters."
      ],
      "action": null
    },
    "mode": "automatic",
    "interactive": false
  },
  "execution": "Browser interface",
  "api": null,
  "browser_agent": {
    "supported": true,
    "name": "run_current_tool",
    "discovery": "WebMCP on the human page in a supporting browser",
    "verification": "See audit/API-AUDIT.md; availability is not verification"
  }
}

Page guide

Convert CSS pixels and rem units in either direction.

How to use PX to REM converter
  1. Enter the values you want to calculate and choose the relevant units or settings.
  2. The result updates as you type. Adjust the available settings if needed.
  3. Review the result, then use Copy result or a download link when available.

Useful next steps

Contrast checkerAspect ratio calculator

How to use it

Enter a value and the root font size. Choose Pixels to rem or Rem to pixels. The default root size is 16px, but you can match your project's CSS.

A worked example

At a 16px root, 24px equals 1.5rem. In the reverse direction, 2rem equals 32px.

What to know

A rem unit is relative to the root element's font size, not the parent element. This calculator does not inspect a webpage or convert em units. Negative values are accepted for properties that support them.