That's just the average in Great Britain, Germany, France, Italy and Spain, according to the numbers from consumer research firm Kantar Worldpanel.
Microsoft's mobile operating system has already crossed a double digit sales share in France with 10.8%. In Great Britain it's a solid 12%, which is a head-turning 7% year-over-year increase.
"Windows Phone's latest wave of growth is being driven by Nokia's expansion into the low and mid-range market with the Lumia 520 and 620 handsets," said Dominic Sunnebo, strategic insight director at Kantar.
"These models are hitting the sweet spot with 16- to 24 year-olds and 35- to 49 year-olds, two key groups that look for a balance of price and functionality in their smartphone."
Windows Phone vs iOS vs Android sales
Microsoft is actually closing the gap between Windows Phone and iOS in some countries.
It's sales share in Germany, for example, is just one percentage point behind iOS.
Android still dominates smartphone sales throughout Europe, maintaining a 70.1% market share. But the report stated that its "dominant position is increasingly threatened" by Windows Phone and iOS growth.
"After years of increasing market share, Android has now reached a point where significant growth in developed markets is becoming harder to find," noted Sunnebo.
"Android's growth has been spearheaded by Samsung, but the manufacturer is now seeing its share of sales across the major European economies dip year on year as a sustained comeback from Sony, Nokia and LG begins to broaden the competitive landscape."
The rest of the globe
Windows Phone's popularity surge hasn't caught on everywhere in the world.
In the U.S., for example, Microsoft's mobile OS only accounted for 3% of smartphone sales in the last three months ending in August. That's a year-over-year increase of just 0.4%.
Sales of Windows Phone devices actually declined to a 2.1% share in China, going 2.6% in the wrong direction. But that's because Android was the only mobile OS to see an increase in the country, taking 9.2% more of the pie for a 72.4% share.
Australia was more kind to Microsoft, registering a 6.5% sales share for Windows Phone, an increase of 2.8%, according to the Kantar numbers.
With Windows Phone and Blackberry in switched positions, the new No. 3 could make a move on Apple's sales share in a couple of countries in the coming months.
- Read our LG Optimus L9 review for a 4G budget phone with Android.