Sample Size Calculator and Confidence Interval

Use the online survey calculator to determine your sample size or your confidence interval. The online sample size calculator helps you to exactly define how big your representative statistical sample should be. Knowing the size of the survey sample allows you to accurately estimate the number of people you should involve in your survey.

Do you need to determine your sample size?

If you need to determine the size of your survey sample, you can use this online calculator. It is a simple and intuitive tool that enables you to know how many respondents you need in your sample. The result is the “representative statistical sample” of your survey. It is called a “sample” because it represents only a part of the total target population that you should involve in your survey.

Population size
If you don’t know, use 20000
It’s the total number of people that your sample represents and that reflects the true population (if you don’t know, write 20,000 as the sample size don’t change for target populations larger than that and the difference is not statistically significant).
Margin of error
5% is a common choice
It’s the margin of error you can accept (5% is a common true percentage). When the percentage is smaller, you’re closer to the exact answer at a given confidence level. However for lower margin you require a larger sample size.
Confidence level
Typical choices are 90%, 95%, or 99%
It’s the confidence level you can accept expressed as a percentage (90%, 95% and 99% are common levels). It’s the percentage that expresses how confident you are with the results. For example, 95% confidence interval means that 19 times out of 20 the results lies within the margin of error.
Response distribution (%)
Leave 50% if you’re not sure. In most cases this parameter has to be set at 50%.
The results you expect for each question (standard deviation). If you leave 50%, you go with the most conservative assumption.
The number of respondents needed is:
377
Minimum recommended size of your sample.
Alternate scenarios
Sample size
Margin of error
9.78%
6.89%
5.62%
Confidence level
Sample size
267
377
643

Do you need to determine your confidence interval?

The confidence interval is a percentage that describes the confidence level of the result obtained with your survey. If you need to calculate the confidence interval, you can use the online calculator on this page. It is a simple and intuitive tool that enables you to define the confidence interval and to know how much sure you can be of the results obtained from your representative sample.
earn more about the confidence interval >

Confidence level
Typical choices are 90%, 95%, or 99%
It’s the confidence level you can accept expressed as a percentage (90%, 95% and 99% are common levels). It’s the percentage that states how confident you are with the results. For example, 95% means that 19 times out of 20 the results lies within the margin of error.
Sample size
Total number of respondents.
Population size
If you don’t know, use 20000
It’s the total number of people that your sample represents (if you don’t know, write 20,000 as the sample size don’t change for larger populations and the difference is not statistically significant).
Response distribution (%)
Leave 50% if you’re not sure. In most cases this parameter has to be set at 50%.
The results you expect for each question (sample standard deviation). If you leave 50%, you go with the most conservative assumption.