Nine ways to understand a rating
Choose your
rating calculator.
Start with the method you need. Each calculator explains its formula, required inputs and limitations.
Arithmetic mean
Every review has equal weight. Calculate your average, reach a target or see how new reviews change it.
Open calculator →Bayesian estimate
Combine your reviews with an adjustable prior. Estimate a rating, target or new-review scenario.
Open calculator →Weighted average
Calculate a star rating with a different weight per review in each group.
Open calculator →Time-decay rating
Estimate a rating that gives recent reviews more weight using an adjustable half-life.
Open calculator →Rating over a time window
Calculate an average using only review groups inside a chosen number of days.
Open calculator →Positive review percentage
Find the percentage of reviews that recommend a product.
Open calculator →Wilson lower bound
Calculate a conservative ranking score from positive and negative review counts.
Open calculator →Median star rating
Find the middle rating from a distribution of one- to five-star reviews.
Open calculator →Trimmed mean rating
Calculate an average after removing an equal share of the lowest and highest ratings.
Open calculator →Mathematical models, clear assumptions
These calculators apply the formulas shown on their pages. Real services may use unpublished weights, review filtering and rounding, so their ratings can differ.
Rating calculation examples
- How many 5-star reviews to reach 4.5 from 100 reviews averaging 4.2?
- How many 5-star reviews to reach a displayed 4.5 from 100 reviews averaging 4.2?
- How many 5-star reviews to reach 4.5 from 100 reviews averaging 4.2? Bayesian estimate (7 prior reviews at 3.5).
- How many 5-star reviews to reach 4.5 from 100 reviews averaging 4.2 (from star counts)?
- What is the rating after adding 1 one-star review to 100 reviews averaging 4.2?