“How many respondents do I need?” is one of the most common questions when writing a thesis, and the answer depends on the size of the population, the confidence you want and the error you are willing to accept. The calculator uses Cochran’s formula, with the finite population correction.
The total number of people you are studying, for example all students at a faculty. Leave it empty if the population is very large or unknown.
The probability that the true value lies within the margin of error.
How far the result may deviate; 5 %, for example, means a range of ±5 percentage points.
If you do not know, leave it at 50 %. That gives the largest sample, so you are on the safe side.
If you expect only some of those invited to reply, enter what share that is. The tool will work out how many questionnaires to send.
The calculation runs in your browser; nothing is sent or stored.
How to read the result
- The sample needed is the number of completed questionnaires, not the number sent out.
- A smaller margin of error needs a larger sample. The difference between 5 % and 3 % often means twice as many respondents.
- Population size matters less than people think. Above a few tens of thousands of units, the sample needed barely changes.
- The calculation holds for a random sample. If you recruit respondents through social media or people you know, the sample is a convenience sample, and that should be stated in the thesis as a limitation.
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Together we will settle the type of sample, design the questionnaire and align the methodology with the aim and hypotheses of your thesis. Send an inquiry with no obligation.
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