Sample Size Calculator
Determine the optimal number of testers for your consumer research study. Get statistically valid results without overspending.
Study Parameters
Enter your research parameters
Total size of your target market or customer base
95% is standard for most research
Acceptable range of error (3-5% is typical)
Use 50% for maximum variance (most conservative)
Product, packaging and shipping per tester, in your own currency. Leave empty to skip the cost estimate.
Recommended Sample Size
Testers Needed
How the formula works, with a worked example. No email needed.
How this is calculated
n₀ = z² · p(1 − p) / e²
n = n₀ / (1 + n₀ / N)
Cochran's formula for a proportion with a finite population correction. z comes from the confidence level (1.645, 1.96 or 2.576), p is the expected distribution, e the margin of error and N the population size. The result is rounded up.
Interpretation Guide
Sample Size
Minimum number of testers for statistical validity
Confidence Level
Probability that results represent the true population
Margin of Error
Expected range of variation in your results
Common rules of thumb by study type
Conventions used in consumer research, not a substitute for the calculation above.
Qualitative Research
Testers
- Focus groups
- In-depth interviews
- Usability testing
Quantitative Research
Testers
- Surveys
- A/B testing
- Concept testing
Product Testing
Testers
- Home usage tests
- CLT (Central Location)
- Sensory testing
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Portifer makes it easy to recruit and manage the exact number of testers you need.
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