Compare calculators

Both calculators run independently — change the inputs on either side to compare results.

Sample Size Calculator

Determine the minimum sample size needed for a survey or experiment given your confidence level, margin of error, and population size. Prevents under-powered studies and over-budgeted data collection.

Population Size (N) (people)

Confidence Level

Margin of Error (%)

Response Distribution

Fill in the required fields to see your result.

Probability

Bayes' Theorem Calculator

Compute the posterior probability P(A|B) from a prior belief, a likelihood, and a false-positive rate. Use it for medical testing, spam filtering, or any scenario where you update beliefs with new evidence.

Prior Probability P(A)

Likelihood P(B|A)

Likelihood P(B|¬A)

Fill in the required fields to see your result.

Key differences

	Sample Size Calculator	Bayes' Theorem Calculator
Category	Probability	Probability
Inputs required	4	3
Result	Required Sample Size (samples)	Posterior Probability P(A\|B)
What it does	Determine the minimum sample size needed for a survey or experiment given your confidence level, margin of error, and population size. Prevents under-powered studies and over-budgeted data collection.	Compute the posterior probability P(A\|B) from a prior belief, a likelihood, and a false-positive rate. Use it for medical testing, spam filtering, or any scenario where you update beliefs with new evidence.