diff --git a/core/src/net/sf/openrocket/rocketcomponent/MassObject.java b/core/src/net/sf/openrocket/rocketcomponent/MassObject.java
index 80ac7c2b6..58adc3f39 100644
--- a/core/src/net/sf/openrocket/rocketcomponent/MassObject.java
+++ b/core/src/net/sf/openrocket/rocketcomponent/MassObject.java
@@ -66,12 +66,12 @@ public abstract class MassObject extends InternalComponent {
 	}
 	
 	
-	public final double getRadius() {
+	public double getRadius() {
 		return radius;
 	}
 	
 	
-	public final void setRadius(double radius) {
+	public void setRadius(double radius) {
 		radius = Math.max(radius, 0);
 
 		for (RocketComponent listener : configListeners) {
diff --git a/core/src/net/sf/openrocket/rocketcomponent/Parachute.java b/core/src/net/sf/openrocket/rocketcomponent/Parachute.java
index 74ffc5f08..e7b2a12c7 100644
--- a/core/src/net/sf/openrocket/rocketcomponent/Parachute.java
+++ b/core/src/net/sf/openrocket/rocketcomponent/Parachute.java
@@ -15,6 +15,7 @@ public class Parachute extends RecoveryDevice {
 	private double diameter;
 	private final double InitialPackedLength = this.length;
 	private final double InitialPackedRadius = this.radius;
+	private boolean autoRadius;
 
 	private Material lineMaterial;
 	private int lineCount = 6;
@@ -145,6 +146,64 @@ public class Parachute extends RecoveryDevice {
 		//// Parachute
 		return trans.get("Parachute.Parachute");
 	}
+
+	@Override
+	public void setRadius(double radius) {
+		radius = Math.max(radius, 0);
+
+		for (RocketComponent listener : configListeners) {
+			if (listener instanceof MassObject) {
+				((MassObject) listener).setRadius(radius);
+			}
+		}
+
+		if (MathUtil.equals(this.radius, radius) && (!autoRadius))
+			return;
+
+		this.autoRadius = false;
+		this.radius = radius;
+		fireComponentChangeEvent(ComponentChangeEvent.MASS_CHANGE);
+	}
+
+	@Override
+	public double getRadius() {
+		if (autoRadius) {
+			if (parent == null) {
+				return radius;
+			}
+			if (parent instanceof NoseCone) {
+				return ((NoseCone) parent).getAftRadius();
+			} else if (parent instanceof Transition) {
+				double foreRadius = ((Transition) parent).getForeRadius();
+				double aftRadius = ((Transition) parent).getAftRadius();
+				return (Math.max(foreRadius, aftRadius));
+			} else if (parent instanceof BodyComponent) {
+				return ((BodyComponent) parent).getInnerRadius();
+			} else if (parent instanceof RingComponent) {
+				return ((RingComponent) parent).getInnerRadius();
+			}
+		}
+		return radius;
+	}
+
+	public boolean isRadiusAutomatic() {
+		return autoRadius;
+	}
+
+	public void setRadiusAutomatic(boolean auto) {
+		for (RocketComponent listener : configListeners) {
+			if (listener instanceof Parachute) {
+				((Parachute) listener).setRadiusAutomatic(auto);
+			}
+		}
+
+		if (autoRadius == auto)
+			return;
+
+		autoRadius = auto;
+
+		fireComponentChangeEvent(ComponentChangeEvent.BOTH_CHANGE);
+	}
 	
 	@Override
 	public boolean allowsChildren() {
@@ -223,26 +282,9 @@ public class Parachute extends RecoveryDevice {
 		//// END Implement parachute packed diameter
 		//// BEGIN Size parachute packed diameter within parent inner diameter
 		if (length > 0 && radius > 0) {
-			double parachuteVolume;
-			double trimPackedRadius = .975;
-			parachuteVolume = (Math.PI * Math.pow(radius, 2) * length);
-
-			if (parent instanceof NoseCone) {
-				radius = ((NoseCone) parent).getAftRadius();
-				length = parachuteVolume / (Math.PI * Math.pow((radius), 2));
-			} else if (parent instanceof Transition) {
-				double foreRadius = ((Transition) parent).getForeRadius();
-				double aftRadius = ((Transition) parent).getAftRadius();
-				double innerRadius = (Math.max(foreRadius, aftRadius));
-				radius = innerRadius * Math.pow((trimPackedRadius), 2);
-				length = parachuteVolume / (Math.PI * Math.pow((radius), 2));
-			} else if (parent instanceof BodyComponent) {
-				radius = ((BodyComponent) parent).getInnerRadius();
-				length = parachuteVolume / (Math.PI * Math.pow((radius), 2));
-			} else if (parent instanceof RingComponent) {
-				radius = ((RingComponent) parent).getInnerRadius();
-				length = parachuteVolume / (Math.PI * Math.pow((radius), 2));
-			}
+			double parachuteVolume = (Math.PI * Math.pow(radius, 2) * length);
+			setRadiusAutomatic(true);
+			length = parachuteVolume / (Math.PI * Math.pow(getRadius(), 2));
 
 		}
 		//// END Size parachute packed diameter within parent inner diameter
diff --git a/swing/src/net/sf/openrocket/gui/configdialog/ParachuteConfig.java b/swing/src/net/sf/openrocket/gui/configdialog/ParachuteConfig.java
index fac72e6fa..dcbcf9ad2 100644
--- a/swing/src/net/sf/openrocket/gui/configdialog/ParachuteConfig.java
+++ b/swing/src/net/sf/openrocket/gui/configdialog/ParachuteConfig.java
@@ -6,6 +6,7 @@ import java.awt.event.ActionListener;
 
 import javax.swing.ComboBoxModel;
 import javax.swing.JButton;
+import javax.swing.JCheckBox;
 import javax.swing.JComboBox;
 import javax.swing.JLabel;
 import javax.swing.JPanel;
@@ -30,6 +31,7 @@ import net.sf.openrocket.rocketcomponent.DeploymentConfiguration;
 import net.sf.openrocket.rocketcomponent.DeploymentConfiguration.DeployEvent;
 import net.sf.openrocket.rocketcomponent.Parachute;
 import net.sf.openrocket.rocketcomponent.RocketComponent;
+import net.sf.openrocket.rocketcomponent.Transition;
 import net.sf.openrocket.rocketcomponent.position.AxialMethod;
 import net.sf.openrocket.startup.Application;
 import net.sf.openrocket.unit.UnitGroup;
@@ -177,7 +179,7 @@ public class ParachuteConfig extends RecoveryDeviceConfig {
 		//// Packed diameter:
 		panel.add(new JLabel(trans.get("ParachuteCfg.lbl.Packeddiam")));
 		
-		DoubleModel od = new DoubleModel(component, "Radius", 2, UnitGroup.UNITS_LENGTH, 0);
+		final DoubleModel od = new DoubleModel(component, "Radius", 2, UnitGroup.UNITS_LENGTH, 0);
 		// Diameter = 2*Radius
 		
 		spin = new JSpinner(od.getSpinnerModel());
@@ -185,7 +187,12 @@ public class ParachuteConfig extends RecoveryDeviceConfig {
 		panel.add(spin, "growx");
 		
 		panel.add(new UnitSelector(od), "growx");
-		panel.add(new BasicSlider(od.getSliderModel(0, 0.04, 0.2)), "w 100lp, wrap 30lp");
+		panel.add(new BasicSlider(od.getSliderModel(0, 0.04, 0.2)), "w 100lp, wrap");
+
+		////// Automatic
+		JCheckBox checkAutoPackedRadius = new JCheckBox(od.getAutomaticAction());
+		checkAutoPackedRadius.setText(trans.get("TransitionCfg.checkbox.Automatic"));
+		panel.add(checkAutoPackedRadius, "skip, span 2, wrap 30lp");
 		
 		
 		//// Deployment