On inheriting a huge fortune when her father died in 1908, she founded a number of boarding schools for needy children known as Sunnerdahls Hemskolor.
From 1914, she made a series of donations to the city of Stockholm for the construction of low-rental apartments to house working-class families with several children.
[1] In 1913, she made a further donation of SEK 500,000 to the Swedish Academy for purchasing the top floors of the Stockholm Stock Exchange Building so that it could hold its meetings there.
In 1914, 1928 and 1935, she made donations to the city of Stockholm for the construction of five residential buildings on Södermalm which needy families with children could rent at reasonable rates.
[1] Magna Sunnerdahl lived on Naravägen [sv] in central Stockholm with her friend and relative Elisabet Lincke who died in 1923.