sample size calculator

How to Use the Krejcie and Morgan Sample Size Calculator?

Enter the total population you are studying, then choose your confidence level and margin of error if you need settings other than the standard 95% confidence level and 5% margin of error. The calculator applies the formula and rounds the result up to the next whole number. 1.

Why Does Population Size Affect Sample Size?

A larger population does not mean you need to survey an equally large percentage of it. The required sample increases as the population grows, but the increase becomes smaller once the population is large. For example, a population of 100 may require about 80 responses, while a population of 1,000 requires about 278.

What Confidence Level Should You Use?

Confidence level describes how confident you want to be that your sample represents the population within the stated margin of error. 90% Confidence Level A 90% confidence level requires a smaller sample than 95% or 99%. It may be appropriate when a less conservative estimate is acceptable.

What Margin of Error Should You Use?

The margin of error represents the amount of sampling error you are willing to accept. A 5% margin of error is a common choice for surveys and general research. A smaller margin of error requires a larger sample. For example, using 3% instead of 5% generally increases the number of responses needed.

What If You Expect Non-Responses?

The calculated sample size refers to completed responses. It does not automatically account for people who decline to participate, leave a survey incomplete, or cannot be reached. If you expect an 80% response rate and need 278 completed responses, you would need to invite approximately 348 people: 278 ÷ 0.80 = 347.5 In practice, round this up to 348 participants.