Pick the decision type
Quantitative decisions (how many customers want X) need a calculated sample size. Qualitative decisions (what does the workflow look like) need enough interviews to reach thematic saturation, not a statistical count.
Free MVP validation calculator
Sample Size Planning Guide
Get a real, formula-based sample size for a survey decision, or a practical interview-count range for a qualitative one.
- Calculated instantly from your inputs
- No signup or data submission
- A focused next step for MVP planning
Your entries remain in this browser session and are not sent to MVPHub.
Your inputs
Choose your decision type and precision
Pick the kind of research decision you are making and the precision you need — the calculator uses the standard margin-of-error formula for quantitative research.
Your calculated result
Your result
0/100
Planning score
Recommended next actions
How it works
Apply the standard formula
For quantitative research the tool uses n = z² × p(1−p) / e², the standard survey sample-size formula, with the most conservative assumption (p=0.5) unless you know your expected response split.
Correct for a small population
If you provide a total population size, a finite population correction reduces the required sample — useful when your addressable market is a known, smaller list rather than the general public.
Frequently asked questions
Why does the calculator use p=0.5?
p=0.5 (a 50/50 split) produces the largest, most conservative required sample size when you do not already know the expected answer distribution — it is the safe default.
What margin of error should I use for an early MVP decision?
A ±10% margin is common for early directional research. Use ±5% or tighter only when the decision carries real financial or funding weight.
Why is the qualitative recommendation not a formula?
Interview research is about discovering the range of themes and workflows, not measuring a numeric proportion — saturation (new interviews stop revealing new information) is the right stopping signal, not a z-score calculation.
What if I cannot reach the calculated sample size?
A smaller sample still gives directional evidence — just report the actual margin of error you achieved, or use the calculator in reverse: fix your realistic sample size and note the margin it implies.
Does the finite population correction always apply?
Only if you provide a population size. For anything above a few tens of thousands, the correction has almost no effect and can be left blank.
How we compare
| Capability | MVPHub | SurveyMonkey Sample Size Calculator | Excel/Google Sheets |
|---|---|---|---|
| Standard margin-of-error formula | ✓ | ✓ | — |
| Finite population correction | ✓ | ✓ | — |
| Qualitative interview-count guidance | ✓ | × | × |
| Built into a broader MVP validation toolkit | ✓ | × | × |
MVPHub applies the same standard formula used by dedicated survey calculators, and adds guidance for qualitative research decisions that a pure statistical calculator does not cover.