# Survey DesignTool for Calculating the Appropriate Sample Size Probably the most frequent question we get is “How many
people do I need to survey to get good results?” It often
comes as a surprise that the number is less than they might expect. Our response is to ask them “Well, what degree of accuracy do you need?” And that level of accuracy is expressed as the margin of error or sampling variation or the degree to which a given response is due to blind luck.Here are some rules of thumb for sample size calculating:Use a confidence level of 95 percent. It’s the standard choice and won’t be questioned.
When you are interested in the results for the total sample and it’s not critical to get reliable results for individual sub-segments, a sample size of 400 will yield a margin of error of +/- 5%.
When you want to have reliable results when comparing specific segments in your sample (e.g., males v. females), you want at least 150 (MoE=8%) to 200 (MoE=7%) surveys for each segment of interest.

### Click on your button choice below to launch the appropriate calculator.

(Click on the button again to close the calculator)

## Sample Size calculator – Means

### Step 1:

Desired confidence level: 99% 95% 90%

### Step 2:

Desired margin of error: ±

### Step 3:

Estimated standard deviation:

### Step 4:

Population size: infinite actual/estimated:
 use ‘infinite’ when the group is larger than 1, or you don’t know the actual size of the overall population

Required Sample Size:

see formula

## Sample Size Calculator – Proportions/Percentages

### Step 1:

Desired confidence level: 99% 95% 90%

### Step 2:

Desired margin of error: ± %

### Step 3:

Estimated proportion (use 50% if unknown): %

### Step 4:

Population size: infinite actual/estimated
 use ‘infinite’ when the group is larger than 1, or you don’t know the actual size of the overall population

Required sample size:

see formula

You will need to have the following data points to calculate your desired sample size: