# Sample Size Calculator and Confidence Interval.

## Do you need to determine your sample size?

### Use our sample size calculator to know how many people you need in your sample.

Population size
If you don’t know, use 20000
Total number of people that your sample represents and reflects the 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
The margin of error you can accept (5% is a common true percentage). It’s the percentage of error you can accept. When the percentage is smaller, you’re closer to the exact answer at a given confidence level but for lower margin you require a larger sample size.
Confidence level
Typical choices are 90%, 95%, or 99%
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:
5055
Minimum recommended size of your sample.
Sample Size Calculator – Alternate scenarios
Sample size
Margin of error
3.5%
3.5%
3.5%
Confidence level
Sample size
3.5%
3.5%
3.5%

## Do you need to determine your confidence interval?

### Use the confidence interval calculator to know how confident you can be with the results you get from the sample you have.

Confidence level
Typical choices are 90%, 95%, or 99%
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% 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
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.