Every business owner has stared at their Google star rating and wondered: how exactly does Google calculate this number? Whether you're sitting at 4.2 and trying to reach 4.5, or defending a hard-earned 4.8, understanding the math behind your rating gives you a strategic advantage.
In this guide, we'll break down the exact formula Google uses, explain how rounding works, and show you why not all reviews impact your score equally.
The Google Review Score Formula
Google calculates your star rating using a weighted average. The formula is straightforward:
Score = (5×five_star + 4×four_star + 3×three_star + 2×two_star + 1×one_star) ÷ total_reviews
For example, if your business has 100 five-star reviews, 25 four-star reviews, 12 three-star reviews, 5 two-star reviews, and 8 one-star reviews:
(5×100 + 4×25 + 3×12 + 2×5 + 1×8) ÷ 150 = 654 ÷ 150 = 4.36
How Google Rounds Your Score
Google displays your rating rounded to one decimal place using standard mathematical rounding. 4.349 rounds down to 4.3, while 4.350 rounds up to 4.4. This means the threshold to reach the next displayed score is actually 0.05 below it. To display 4.5, your raw score only needs to reach 4.45.
Why Some Reviews Matter More Than Others
The fewer reviews you have, the more each new review impacts your score. A business with 20 reviews loses 0.2 points from one 1-star review, while a business with 500 reviews barely moves.
What Google Doesn't Factor In
Recency doesn't affect the score calculation. Review text doesn't matter — only the star count. Owner responses don't change the mathematical score. Review helpfulness votes don't affect the calculation.
The Practical Takeaway
Know your numbers with our free Google review calculator. Focus on volume. Target the threshold. Don't panic over one bad review if you have 100+ reviews.