CSAT Confidence Interval Calculator
Your CSAT score is a sample, not the ground truth. The Wilson score interval tells you — with 95% confidence — what your true satisfaction rate probably is. A 92% score from 50 ratings is much less certain than a 92% score from 500.
Why your CSAT score is a range
Your actual CSAT is a sample, not the true population score. With Wilson scoring we can say with 95% confidence what the true underlying satisfaction rate likely is. Small samples → wide ranges.
Observed CSAT
84.0%
84 of 100 ratings
95% confidence interval (Wilson score)
With 95% confidence, your true CSAT falls between 76%–90%.
Track CSAT in real time with SupportmanThe naive confidence interval (p ± z√(p(1-p)/n)) breaks down at the edges. When your CSAT is 95% from 10 ratings, the simple formula can suggest the upper bound is above 100% or the lower bound is negative. Wilson score handles these cases correctly.
Rule of thumb: You need roughly 100 ratings to have a confidence interval narrower than ±5 percentage points at 95% confidence. Below 30 ratings, the range is wide enough that month-to-month comparisons are mostly noise.
What to do with a wide interval: Collect more ratings (improve survey response rate), or acknowledge that your CSAT number is directional rather than precise. A team with 50 ratings reporting 90% CSAT and a team with 500 ratings reporting 88% CSAT may be performing identically.