Wpf: Grid: How can i share column/row height width?

I know this is an old question, but I'll answer for anyone who stumbles across this while googling.

There's actually a very simple solution to this problem, using the SharedSizeScope mentioned by Quartermeister.

<Grid IsSharedSizeScope="True">
    <Grid.RowDefinitions>
        <RowDefinition Height="Auto" SharedSizeGroup="groupName" />
        <RowDefinition Height="Auto" SharedSizeGroup="groupName" />
        <RowDefinition Height="Auto" SharedSizeGroup="groupName" />
    </Grid.RowDefinitions>

    ...
</Grid>

Just make sure you set Grid.IsSharedSizeScope to true, and make sure that each RowDefinition has the same SharedSizeGroup, and the rows should be auto and equally sized. This works for columns as well.

Ideally you would use rows with star sizing as you have and set the Grid to VerticalAlignment="Top", but unfortunately star sizing doesn't work when the grid sizes to its content.

Instead of using a single Grid, use a UniformGrid for the vertical layout with nested Grid controls for horizontal layout. You can set a SharedSizeScope on the columns in the inner grids so that the column sizing is shared between them.

<UniformGrid Rows="5" VerticalAlignment="Top" Grid.IsSharedSizeScope="True">
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition SharedSizeGroup="A"/>
            <ColumnDefinition SharedSizeGroup="B"/>
            <ColumnDefinition SharedSizeGroup="C"/>
        </Grid.ColumnDefinitions>

        <Label Grid.Column="0">Gas Volume Fraction</Label>
        <TextBox Grid.Column="1" Text="{Binding Path=GasVolumeFraction}" MinWidth="40"></TextBox>
        <Label Grid.Column="2">-</Label>
    </Grid>
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition SharedSizeGroup="A"/>
            <ColumnDefinition SharedSizeGroup="B"/>
            <ColumnDefinition SharedSizeGroup="C"/>
        </Grid.ColumnDefinitions>

        <Label Grid.Column="0">Density</Label>
        <TextBox Grid.Column="1" Text="{Binding Path=Density}" MinWidth="40"></TextBox>
        <Label Grid.Column="2">kg/m3</Label>
    </Grid>
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition SharedSizeGroup="A"/>
            <ColumnDefinition SharedSizeGroup="B"/>
            <ColumnDefinition SharedSizeGroup="C"/>
        </Grid.ColumnDefinitions>
        <Label Grid.Column="0" Content="Curve speed" Style="{StaticResource curveSpeed}"></Label>
        <TextBox Grid.Column="1" Text="{Binding Path=Density}" Style="{StaticResource curveSpeed}" MinWidth="40"></TextBox>
        <Label Grid.Column="2" Style="{StaticResource curveSpeed}">rpm</Label>
    </Grid>
    <WrapPanel>
        <RadioButton>Delta pressure</RadioButton>
        <RadioButton>Head</RadioButton>
    </WrapPanel>
    <WrapPanel>
        <RadioButton>Efficiency</RadioButton>
        <RadioButton>Power</RadioButton>
        <RadioButton>Torque</RadioButton>
    </WrapPanel>
</UniformGrid>