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Calculate the size of scrollbar

Written byPhuoc Nguyen
Level 2 — Intermediate
03 Mar, 2020
Last updated
11 Sep, 2022

1. Subtract `clientWidth` from `offsetWidth`

The `clientWidth` property indicates the width without scrollbar. The `offsetWidth`, on the other hand, includes the scrollbar if there is.
Here is the simple calculation to determine the width of scrollbar:
const scrollbarWidth = document.body.offsetWidth - document.body.clientWidth;

2. Use a fake element

We create two fake `div` elements, one of them is the child of the other. Then calculate the difference between their widths.
const calculateScrollbarWidth = function () {
// Create the parent element
const outer = document.createElement('div');
outer.style.visibility = 'hidden';
outer.style.overflow = 'scroll';

// Append it to `body`

// Create the child element
const inner = document.createElement('div');

// Calculate the difference between their widths
const scrollbarWidth = outer.offsetWidth - inner.offsetWidth;

// Remove the parent element

return scrollbarWidth;
This method doesn't work on macOS if the Show scroll bars option is set as Automatically based on mouse or trackpad or When scrolling.
Show scroll bars option on macOS
Show scroll bars option on macOS

See also

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Phước Nguyễn