Margin of Error Calculator

What is the Margin of Error Calculator?

Calculate the margin of error for a survey or poll. Margin of error shows how far a survey result may be from the true population value, which is essential for reporting results honestly.

How to use the Margin of Error Calculator

1. Enter your sample size, your confidence level, your observed proportion.
2. Results update automatically as you type; you can also press Calculate.
3. Read the output: margin of error, confidence interval.
4. Use the 📊 chart to see the result visually, then copy or share it.

Formula and method

Worked example

With sample size = 1,000, confidence level = 95%, observed proportion = 50 %, the Margin of Error Calculator returns margin of error: ±3.10%; confidence interval: 46.90% – 53.10%.

Where the Margin of Error Calculator helps in real life

You surveyed 400 customers and 62% said they would recommend you. The calculator shows a margin of about ±4.8% at 95% confidence, so the true figure is likely between about 57% and 67%.

You are reading a news poll that shows two candidates two points apart. Checking the margin of error shows whether the gap is meaningful or within the noise.

Common mistakes to avoid

• Thinking a small margin fixes a biased sample.
• Reporting a result without its confidence level.
• Treating overlapping ranges as a clear difference.
• Applying the formula to self-selected online polls.

💡 Practical tip: Larger samples reduce the margin of error, but no sample size can fix a biased way of choosing respondents.

Tips for better results

• Quadruple the sample size to halve the margin of error.
• Report results as a range, not a single number.
• Use random sampling whenever possible.

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