Survey Size Calculator
Enter the population size, the margin of error, the confidence level and the response rate you expect. The calculator gives the responses you need and how many people to invite.
- Responses needed
- Invitations
- Margin of error
If you have no idea of the answer split, 50% is the safest guess and is used here.
Responses needed depend on accuracy, not population, once the population is large. For a population of 10,000 at ±5% and 95% confidence you need 370 responses. With a 20% response rate, invite about 1,850 people.
Survey size chart
95% confidence. Search for a population.
| Population | ±3% | ±5% | ±10% |
|---|---|---|---|
| 100 | 92 | 80 | 50 |
| 500 | 341 | 218 | 81 |
| 1,000 | 517 | 278 | 88 |
| 5,000 | 880 | 357 | 95 |
| 10,000 | 965 | 370 | 96 |
| 100,000 | 1056 | 383 | 96 |
| Very large | 1068 | 385 | 97 |
Responses.
Margin and responses
95% confidence, large population. Slide the margin of error.
Lit dots are the replies you need.
How to size a survey
Accuracy to invitations. Step through it.
Population
Size.
Send reminders to lift the response rate.
±3%, ±5% or ±10%
Margins. Compare them.
Precise.
Standard.
Rough.
Halving the margin needs about four times as many responses.
Before you send
Survey checks. Tick each item.
Tick each item as you go.
Pilot the survey on a few people first.
What you get
Survey sizing. Each tile explains one result.
Needed.
To send.
±%.
Level.
Twice as good.
A random, unbiased sample matters more than a huge one.
Frequently Asked Questions
No question matches that search.
How many survey responses do I need?
About three hundred and eighty five for plus or minus five per cent at ninety five per cent confidence in a large population.
How many people should I invite?
Divide the responses needed by the response rate you expect.
Does population size matter?
Only when it is small. Above about twenty thousand it barely changes the answer.
What is a margin of error?
How far the survey result may be from the true value.
What confidence level should I use?
Ninety five per cent is the usual choice.
What is a good response rate?
Online surveys often get ten to thirty per cent.
What if I need more invitations than people?
Survey everyone or accept a wider margin of error.
Ask enough people
Plan your responses and invitations up front and your survey results stand up.
More size calculators
Each one has its own calculator, worked examples and answers to common questions.