Kalla had herself said she was in good shape ahead of the 10km freestyle distance, her favourite race.
Poor conditions, including warm temperatures and heavy snow, worked in her favour as the Swedish team had obviously chosen the right wax for the skis, meaning Kalla could pull away from her rivals. Surprising silver and bronze medallists were Jessica Diggins and Caitlin Gregg from the USA.
"I can hardly believe it's true. Winning the world championships in this distance here in Sweden, it's amazing", she told Swedish TV after the race.
The other Swedish competitors were Maria Rydqvist, Emma Wikén and Jennie Öberg. They finished 4th, 16th and 37th respectively.