FULL PRODUCT VERSION :
java version "1.8.0_131"
Java(TM) SE Runtime Environment (build 1.8.0_131-b11)
Java HotSpot(TM) 64-Bit Server VM (build 25.131-b11, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 10.0.15063]

A DESCRIPTION OF THE PROBLEM :
If the font size of a parent is specified in pt values in css, children with font sizes specified in em values will not always be correct.

For example, if a pane has two children, panes A and B. Each of them contain a Text. If you set the font size of the root pane to 8pt in css and the font size of pane A to 1em in css, you would expect both labels to have the exact same size since 1em = font size (according to modena.css).

With some font sizes, this is true, but with others there are fairly significant errors.

Tested on jdk-9+181 and 8.131

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Select a font size to test, and run the application.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Every label should have the exact same font size.
ACTUAL -
The font size for the 1em label is 10.69 while the font size for the label that inherits its font size from the root pane is 10.66.

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
package fontsizetest;

import javafx.application.Application;
import javafx.beans.binding.Bindings;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.layout.VBox;
import javafx.scene.text.Text;
import javafx.stage.Stage;

/**
 *
 * @author Dean
 */
public class FontSizeTest extends Application {

    @Override
    public void start(Stage primaryStage) {
        int levels = 5;
        VBox root = new VBox();
        root.setStyle("-fx-font-size:8pt");
        VBox A = new VBox();
        VBox B = new VBox();
        A.setStyle("-fx-font-size:1em;");
        Text textA = new Text("Text Test");
        Text textB = new Text("Text Test");

        Label labelAFont = new Label();
        Label labelBFont = new Label();
        labelAFont.textProperty().bind(Bindings.concat("Text A Font: ", textA.fontProperty().asString()));
        labelBFont.textProperty().bind(Bindings.concat("Text B Font: ", textB.fontProperty().asString()));
        Label labelABounds = new Label();
        Label labelBBounds = new Label();
        labelABounds.textProperty().bind(Bindings.concat("Text A Bounds: ", textA.layoutBoundsProperty().asString()));
        labelBBounds.textProperty().bind(Bindings.concat("Text B Bounds: ", textB.layoutBoundsProperty().asString()));

        A.getChildren().addAll(textA, labelAFont, labelABounds);
        B.getChildren().addAll(textB, labelBFont, labelBBounds);
        root.getChildren().addAll(A, B);
        Scene scene = new Scene(root, 600, 250);

        primaryStage.setTitle("Font Size Test");
        primaryStage.setScene(scene);
        primaryStage.show();

    }

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        launch(args);
    }

}
---------- END SOURCE ----------