How can I change the size of my Dash Graph?

A Graph object contains a figure. Each figure has data and layout attributes.

You can set the height in the layout.

dcc.Graph(
    id="my-graph",
    figure={
        "data": [
            {"x": [1, 2, 3], "y": [4, 1, 2], "type": "bar"},
            {"x": [1, 2, 3], "y": [2, 4, 5], "type": "bar"},
        ],
        "layout": {
            "title": "My Dash Graph",
            "height": 700,  # px
        },
    },
)

According to the Plotly figure object schema, height must be a number greater than or equal to 10, and its default is 450 (px).

Keep in mind that you can create a Graph object and set figure later, in a dash callback.

For example, if the value of a dcc.Slider affects the figure attribute of your Graph you will have:

import plotly.graph_objs as go

dcc.Graph(id="my-graph")

@app.callback(
    output=Output("my-graph", "figure"),
    inputs=Input("slider", "value")])
def update_my_graph(value):
    data = go.Data(
        [
            go.Bar(x=[1, 2, 3], y=[4, 1, 2]),
            go.Bar(x=[1, 2, 3], y=[2, 4, 5]),
        ]
    layout = go.Layout(
        title="My Dash Graph",
        height=700
        )
    figure = go.Figure(data=data, layout=layout)
    return figure

I did this by placing the plot's div as a sub-div inside a parent div, then setting the size of the parent div. Something like this:

# main parent div for the app
main_div = html.Div(children = [
    # sub-div for the plot
    html.Div(children = [
                dcc.Graph(id = 'my-plot'),
    ])
    ],
    # set the sizing of the parent div
    style = {'display': 'inline-block', 'width': '48%'})

As your app grows in complexity you will probably need to set up more div nesting for this to work. And you could also probably just set the style on the plot's sub-div directly, depending on how you've configured things.

Also, I might suggest following the official Dash forums here since there will probably be more users there, along with the Dash dev himself posting frequently: https://community.plot.ly/c/dash

Alternatively, you can change the viewport sizing in the parent container like:

dcc.Graph(id='my-graph',style={'width': '90vh', 'height': '90vh'}) 

That will change the graph to be 90% of the viewport height of the browser. You can see more info of viewport on this link.