code: public static function getDefaultColumnWidthByFont(\PhpOffice\PhpSpreadsheet\Style\Font $font, $pPixels = false)
      {
          if (isset(self::$defaultColumnWidths[$font->getName()][$font->getSize()])) {
              // Exact width can be determined
              $columnWidth = $pPixels ?
                  self::$defaultColumnWidths[$font->getName()][$font->getSize()]['px']
                      : self::$defaultColumnWidths[$font->getName()][$font->getSize()]['width'];
          } else {
              // We don't have data for this particular font and size, use approximation by
              // extrapolating from Calibri 11
              $columnWidth = $pPixels ?
                  self::$defaultColumnWidths['Calibri'][11]['px']
                      : self::$defaultColumnWidths['Calibri'][11]['width'];
              $columnWidth = $columnWidth * $font->getSize() / 11;
  
              // Round pixels to closest integer
              if ($pPixels) {
                  $columnWidth = (int) round($columnWidth);
              }
          }
  
          return $columnWidth;
      }
docs: Get the effective column width for columns without a column dimension or column with width -1
  For example, for Calibri 11 this is 9.140625 (64 px).
  
  @param \PhpOffice\PhpSpreadsheet\Style\Font $font The workbooks default font
  @param bool $pPixels true = return column width in pixels, false = return in OOXML units
  
  @return mixed Column width