Free Tools
Free, fast, no-account calculators for researchers, fieldwork teams, and interviewers.
General calculators
Percentage Calculator
Percentages, increases, decreases, changes and discounts — fast, free and accurate.
Average Calculator
Find the arithmetic mean of any list of numbers.
Ratio Calculator
Simplify a ratio to its lowest terms.
Proportion Calculator
Solve a ÷ b = c ÷ x for the missing term.
Time Duration Calculator
Find hours and minutes between two times.
Date Difference Calculator
Count calendar days between two dates.
Research tools
Sample Size Calculator
Find how many respondents you need for accurate survey results.
Margin of Error Calculator
Estimate the sampling error in your survey results.
Response Rate Calculator
Measure how many invited people completed your survey.
Completion Rate Calculator
Measure how many started surveys were finished.
Incidence Rate Calculator
Find the share of screened respondents who qualify.
Sampling Interval Calculator
Pick every k-th unit for systematic sampling.
Operations tools
Workforce Utilization Calculator
See how much of your team's available time is productive.
Capacity Calculator
Estimate how many tasks a team can complete.
Productivity Calculator
Measure output per hour of work, in any unit.
SLA Compliance Calculator
See how many cases meet their service level agreement.
Turnaround Time Calculator
Measure elapsed time from start to completion.
Cost Per Task Calculator
Find the average operational cost of a task.
Academic & research tools
Citation Generator
Create APA, MLA, Chicago, Harvard or IEEE citations.
Mean / Median / Mode Calculator
Find the mean, median and mode of any set of numbers.
Standard Deviation Calculator
Measure spread with population or sample standard deviation.
Confidence Interval Calculator
Estimate a confidence interval for a proportion.
P-Value Calculator
Compute a p-value for a z or t test.
Statistical Significance Calculator
Compare control vs variant in an A/B test.
Correlation Calculator
Measure the linear relationship between two variables.
Regression Calculator
Fit a simple linear regression line y = a + bx.
NPS Calculator
Calculate your Net Promoter Score from −100 to +100.
Reading Time Calculator
Estimate how long it takes to read any text.
T-Test Calculator
Run one-sample, independent or paired t-tests.
Chi-Square Test Calculator
Test goodness of fit or independence with χ².
ANOVA Calculator
Compare three or more group means with one-way ANOVA.
Effect Size Calculator
Measure effect size with Cohen's d.
Statistical Power Calculator
Estimate statistical power and required sample size.
Outlier / Grubbs' Test Calculator
Detect a single suspected outlier with Grubbs' test.
Z-Test Calculator
Run a z-test for a mean or a proportion.
Statistical Test Selector
Find which statistical test fits your design.
Explore research guides
Practical guides on choosing a statistical test, sample size, p-values, confidence intervals and more.