How many survey responses do you actually need?
Before you send a survey, you need one number: how many completed responses make the result trustworthy. This planner computes it from your population size, confidence level, and margin of error, then reveals the counterintuitive part: a population twenty times larger needs barely any extra responses.
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After you install, this is the model to open.
Survey Sample Size Planner
- In your spreadsheet, click the Sortia icon in the strip of icons down the right-hand edge. No strip? Click the arrow at the bottom-right to open it. You can also use Extensions, then Sortia, then Open Sortia.
- Click Start from a template and put that name in the search box.
- Pick the card with that name and click Load this template. It arrives on a new tab with real numbers already in it.
The answer
With the defaults (5,000 people, 95% confidence, ±5% margin), the sheet returns:
- Responses needed
- 357 for a population of 5,000 at ±5%
- Invitations to send
- 1,190 at a 30% response rate
- Needed at 100,000 people
- 383 only 26 more responses
- Needed at ±3% margin
- 880 precision costs more than population
For a population of 5,000, you need 357 completed responses to report a result at 95% confidence within ±5%. Grow the population to 100,000 and the requirement rises to just 383, because sample size is driven by precision, not population. Tighten the margin to ±3% and the requirement jumps to 880. Plan invitations, not just responses: at a 30% response rate you should send about 1,190.
The model
Five inputs drive the two textbook sample-size formulas, the exact Cochran calculation with a finite-population correction and the Yamane shortcut as a sanity check.
| Population size | 5,000 people |
| Confidence level | 95% (z = 1.96) |
| Margin of error | ±5% |
| Expected answer split | 50 / 50 (safest assumption) |
| Survey response rate | 30% |
Once it is in your sheet
- The model arrives with real numbers in it and runs as it stands, so you can press the button first and understand it second.
- Change the numbers to yours. The sheet marks which cells are inputs and which hold formulas, and most labels carry a note explaining the row.
- Press the run button at the bottom of the panel. It is labeled for the tool you are in, and the result lands on its own tab, with a written reading of it beside the figures.
Never used Google Sheets? Start here goes the whole way, in seven steps, and assumes nothing.
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Every model like this one, and the method behind them: What-if analysis in Google Sheets.