In The Vikings course from The Great Courses, Prof. Kenneth Harl guesses the population in the Scandinavian areas (which would become Norway, Denmark, and Sweden) from around 800 A.D. through around 1100 A.D. was something in the range of 800,000 to 1,000,000 people. He thinks migration to Ireland, England, and Iceland offset the natural population growth.

In Vikings at War by Kim Hjardar and Vegard Vike makes the following guesses for population at location 525 in Kindle edition:

• Denmark –
•      500,000 – 1100 A.D.
• Norway –
•      100,000 to 150,000 – 800
•      200,000 – 1000
• Sweden –
•     400,000 – 1000

That would be somewhere around 1,100,000 in the 1000 or 1100 timeframe.

Their estimate includes men and women, inclusive of slaves.