Margin of Error Calculator estimates how wide a survey percentage might swing before you field the study. Use it when you are choosing a sample size and want a ± range at a confidence level you pick. In this article you will learn how to enter sample size and settings, then read the margin of error.
The tool is at form.ms/tools/margin-of-error-calculator.
1. Open the calculator
Go to the Margin of Error Calculator. Margin of error is about ± percentage points around your estimate.
2. Enter sample size and settings
Type Sample size (n) as the completes you expect, not invitations sent. Leave Expected proportion at 50% when you are unsure. That gives the widest (safest) margin. Pick 90%, 95%, or 99% confidence. Population size is optional when you sample a large share of a known group.
3. Read the ± margin
The page shows the half-width in percentage points. Use it to check whether your planned n is precise enough before you launch.
After you have real yes/success counts, use the Confidence Interval Calculator. That tool uses Wilson intervals on actual results, not a planning formula.
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