Skip to main content
Calcimator

Power Analysis Calculator

Calculate the required sample size for a study given the effect size, significance level, and desired statistical power.

Inputs

Results

Required Sample Size (per group)

32

Total Subjects Needed

32

Z-Alpha (two-tailed)1.96
Z-Beta0.84
Actual Power Achieved0.81
Effect Size Used0.5
How to Use This Calculator
  1. Enter Effect Size (Cohen, Significance Level (α), and Statistical Power (1-β).
  2. Set Test Type (1=one-sample, 2=two-sample, 3=paired).
  3. Review Required Sample Size (per group) and Total Subjects Needed.
  4. Use Z-Alpha (two-tailed) and Z-Beta to inform your decision.
  5. Use the chart to visualize the results and explore different scenarios by adjusting inputs.

How the result changes with Statistical Power (1-β)

Statistical Power (1-β)Required Sample Size (per group)Total Subjects Needed
0.551818
0.682424
0.823434
0.955252

What each input means

Effect Size (Cohen's d)
Expected standardized effect size. Small=0.2, Medium=0.5, Large=0.8.
Significance Level (α)
Probability of rejecting a true null hypothesis (Type I error rate). Common: 0.05.
Statistical Power (1-β)
Probability of detecting an effect when it exists. Common: 0.80 or 0.90.
Test Type (1=one-sample, 2=two-sample, 3=paired)
1 = One-sample t-test, 2 = Two-sample t-test (per group), 3 = Paired t-test.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Effect Size (Cohen's d) = 0.5, Significance Level (α) = 0.05, Statistical Power (1-β) = 0.8, Test Type (1=one-sample, 2=two-sample, 3=paired) = 1 = 4 input(s) provided
  2. Calculate Required Sample Size
    32 = 32
  3. Calculate Total Subjects Needed
    32 = 32
  4. Calculate Z-Alpha
    Z-Alpha
    1.9604 = 1.9604
  5. Calculate Z-Beta
    Z-Beta
    0.8415 = 0.8415

Engine last updated . Checked against 2 independently-derived tests — how we verify calculators.

Related Calculators

The questions that sit next to this one — chosen by subject, including calculators filed under a different category.

Statistics

Effect Size Calculator

Calculate Cohen's d, Hedges' g, and Glass's delta to measure the practical significance of differences between two groups.

Statistics

T-Test Calculator

Calculate the t-statistic, degrees of freedom, and approximate p-value for a one-sample t-test.

Statistics

Sample Size Calculator

Determine the required sample size for your survey or study. Calculate how many responses you need for statistically significant results.

Education & Academics

Study Schedule Calculator

Create a study schedule based on total hours needed and days available. Plan your study sessions effectively.

More in Math & Statistics.