how to set QGraphicstextitem's height in mm?

[Selvajothi]

code to add QGraphicstextitem

QFont font;
font.setFamily(defaultFamily);
font.setPointSizeF(defaultTxtsize* mmtopt);
QGraphicstextItem* textitem = new QGraphicstextItem();
textitem->pointSize = defaultTxtsize;
textitem->setPlainText(textEdit->text());
textitem->setFont(font);            
textitem->setDefaultTextColor(defaultColor);
textitem->setPos(gridPosition.x()-5,gridPosition.y()-7);
textitem->setTextInteractionFlags(Qt::TextEditable);
addItem(textitem);

code to export to pdf:

printer = new QPrinter(QPrinter::HighResolution);
printer->setOutputFormat(QPrinter::PdfFormat);
printer->setOutputFileName(pdfFile);//pdfFile contains the name of the  pdf which we have to print
printer->setPageSize(QPrinter::A3);
printer->setOrientation(QPrinter::Landscape);
printer->setPdfVersion(QPagedPaintDevice::PdfVersion_1_6);
QPainter painter(printer);
painter.setRenderHint(QPainter::Antialiasing);
scene->setBackgroundBrush(QBrush(Qt::white));
scene->render(&painter);


//defaultTxtsize = input given by the user in mm
mmtopt = 2.83465(factor to convert mm to points)

I want to add QGraphicsTextitem with its height measured in millimeter, export it to pdf and print it. After printing I checked using ruler manually and there is difference in text height(user input is 2 mm and in paper it shows 1mm). can anyone help me to find out the mistake.

[Asperamanca]

@Selvajothi said in how to set QGraphicstextitem's height in mm?:

font.setPointSizeF(defaultTxtsize* mmtopt);

You got your units mixed up. Point size is given in 1/72 inch. So if you want your text to be 2 mm high, you just need to convert 2 mm to inch and multiply by 72

[Selvajothi]

I have changed as u mentioned and printed it in paper. Still it is not giving the correct height when measured using ruler.

font.setPointSizeF(defaultTxtSize0.039370172)

Here defaultRxtSize is 10mm for the attached image.