How it works
n0 = z^2 p(1-p)/e^2; margin e = z sqrt(p(1-p)/n). Round up; shrink n when population N is known.
n=z^2 p(1-p)/e^2 · e=z sqrt(p(1-p)/n) · n_fpc=n0/(1+(n0-1)/N)
When to use
Use this tool when you need to: calc.net classic: 95% confidence, 5% margin, p=50% → about 385 people. Try margin-of-error mode with n=385 to verify ~5%.
How to use this tool
- Enter your values in the fields above.
- Review the formula and any mode options for your problem.
- Read the result and the step-by-step solution.
Calc.net classic: 95% confidence, 5% margin, p=50% → about 385 people. Try margin-of-error mode with n=385 to verify ~5%.
Frequently asked questions
- What is the Sample Size Calculator?
- n0 = z^2 p(1-p)/e^2; margin e = z sqrt(p(1-p)/n). Round up; shrink n when population N is known.
- How do I use the Sample Size Calculator?
- Enter the required values, then calculate. The Sample Size Calculator shows results, formulas, and step-by-step work when available. No account is required.
- What formula does the Sample Size Calculator use?
- n=z^2 p(1-p)/e^2 · e=z sqrt(p(1-p)/n) · n_fpc=n0/(1+(n0-1)/N)
- Average CalculatorArithmetic and weighted mean with a visual sum÷count layout and step-by-step work.
- Mean, Median, Mode, Range CalculatorArithmetic mean, median, mode(s), and range for comma-separated data — with ordered list, frequency table, and worked steps.
- Statistics CalculatorArithmetic and geometric means, σ and s, variance, quartiles, IQR, and Σx / Σx² from a comma-separated list.
- Standard Deviation CalculatorPopulation σ and sample s with variance, mean, sum, standard error, and margin of error for the mean.
- Number Sequence CalculatorArithmetic, geometric, and Fibonacci sequences: nth term, partial sum, and term list with clear formulas.
- Probability CalculatorIndependent two-event probabilities, solver, series of trials, normal range area, simple favorable/total, and Bayes.