ToolsStatistics
Wilson Score Calculator
Enter your 1-to-5 star counts and get the Wilson lower bound, the statistically honest floor of your true rating. See how many reviews you need to reach a target rating.
Your star counts
Wilson lower bound
- Reviews counted
- Mean rating
- The mean overstates you by
- Reviews to hold 4.5 at this quality
Common questions
What is the Wilson score and why does it matter for product ratings?
The Wilson score is the lower bound of the 95% confidence interval for your true rating. A product with 4.9 stars from four reviews and one with 4.7 stars from 400 reviews are not equally trustworthy. The Wilson score accounts for sample size, so a well-reviewed product ranks above one with suspiciously few reviews even if the average looks higher.
How is the Wilson score calculated for star ratings?
Star ratings are normalised to a 0-to-1 scale before applying the standard Wilson interval formula. A 5-star rating maps to 1.0 and a 1-star rating maps to 0.0. The formula then produces a lower confidence bound at the 95% level, which is scaled back to a 1-to-5 range for readability.
How many reviews do I need to reach my target rating?
The calculator estimates how many additional 5-star reviews are needed to bring your Wilson lower bound to a target value, assuming future reviews match a mix weighted toward positive. This is an estimate, and actual results depend on the rating distribution of reviews you actually receive.