PHPOffice / PhpSpreadsheet

        // Calculate column width in pixels. We assume fixed glyph width. Result varies with font name and size.

        switch ($fontName) {

            case 'Calibri':

                // value 8.26 was found via interpolation by inspecting real Excel files with Calibri 11 font.

                $columnWidth = (int) (8.26 * StringHelper::countCharacters($columnText));

                $columnWidth = $columnWidth * $fontSize / 11; // extrapolate from font size

                break;

            case 'Arial':

                // value 8 was set because of experience in different exports at Arial 10 font.

                $columnWidth = $columnWidth * $fontSize / 11; // extrapolate from font size

                break;

            case 'Arial':

                // value 8 was set because of experience in different exports at Arial 10 font.

                $columnWidth = (int) (8 * StringHelper::countCharacters($columnText));

                $columnWidth = $columnWidth * $fontSize / 10; // extrapolate from font size

                break;

            case 'Verdana':

                // value 8 was found via interpolation by inspecting real Excel files with Verdana 10 font.

                $columnWidth = (int) (8 * StringHelper::countCharacters($columnText));

                $columnWidth = $columnWidth * $fontSize / 10; // extrapolate from font size

                $columnWidth = $columnWidth * $fontSize / 10; // extrapolate from font size

                break;

            case 'Verdana':

                // value 8 was found via interpolation by inspecting real Excel files with Verdana 10 font.

                $columnWidth = (int) (8 * StringHelper::countCharacters($columnText));

                $columnWidth = $columnWidth * $fontSize / 10; // extrapolate from font size

                break;

            default:

                // just assume Calibri

                $columnWidth = $columnWidth * $fontSize / 10; // extrapolate from font size

                break;

            default:

                // just assume Calibri

                $columnWidth = (int) (8.26 * StringHelper::countCharacters($columnText));

                $columnWidth = $columnWidth * $fontSize / 11; // extrapolate from font size

                break;

        }

        // Calculate approximate rotated column width