@tomaschku said in Get Value of DoubleSpinBox into a double or float: Code for checking Values: ui->text_result->setText("Error! " + QVariant(a).toString() + "|" + QVariant(b).toString()); when I edit the Values with the DoubleSpinBoxes, then the Value a doesn't change. (i.e. It's 0.) I think the problem is even worse than what is mentioned above. double a = ui->input_a->value(); does not imply that when input_a changes it automatically updates a