How Many Reviews to Move From 3.9 to 4.0?
You need your average to reach 3.95. From 3.9 the gap is small, so it is usually only a handful of fives, unless you have a very large review count.
Rough guide: with 50 reviews at a true 3.9 average, about 5 to 8 straight five-star reviews tips you to 4.0. With 200 reviews it takes proportionally more.
Related guidesHow Many Google Reviews Do I Need to Reach 4.5 Stars? →How Many Five-Star Reviews Cancel Out a One-Star Review? →How Does Google Calculate a Business’s Star Rating? →Does Google Round Review Ratings Up or Down? →