Methodology and sources
How Studyfigure calculators work, and where their numbers come from.
How the calculators are built
Each calculator runs entirely in your browser; nothing you type is sent anywhere. Results are rounded only for display, and every page shows the formula it uses and a worked example you can check by hand.
How the statistics are computed
The p-value and confidence interval calculators compute the normal, Student’s t and chi-square distributions directly rather than reading from a printed table. The t distribution uses the regularized incomplete beta function, the normal and chi-square distributions use the regularized incomplete gamma function, and critical values come from inverting those functions numerically. Each was checked against the NIST/SEMATECH e-Handbook of Statistical Methods tables: for example z = 1.96 gives a two-tailed p of 0.0500, t = 2.228 with 10 degrees of freedom gives 0.0500, and a chi-square of 3.841 with 1 degree of freedom gives 0.0500.
How rounding is shown
Calculators keep full precision while they work and round only the numbers they display. The significant figures calculator works on the digits you type, not on a rounded binary number, so trailing zeros and exact halves are handled the way a chemistry textbook does.
By calculator
| Calculator | Based on | Last checked |
|---|
| Cumulative GPA calculator | University of Pennsylvania, College of Arts and Sciences: Grade point average, University of Tennessee One Stop: Grades, GPA and levels of distinction, College Board BigFuture: How to convert your GPA to a 4.0 scale | October 28, 2026 |
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| Standard deviation calculator | NIST/SEMATECH e-Handbook of Statistical Methods, 1.3.5.6 Measures of Scale, OpenStax Introductory Statistics 2e, 6.1 The Standard Normal Distribution, Microsoft Support: STDEV.S function | October 28, 2026 |
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| P-value calculator | NIST/SEMATECH e-Handbook, 1.3.6.7.1 Cumulative Distribution Function of the Standard Normal Distribution, NIST/SEMATECH e-Handbook, 1.3.6.7.2 Critical Values of the Student’s t Distribution, NIST/SEMATECH e-Handbook, 1.3.6.7.4 Critical Values of the Chi-Square Distribution | October 28, 2026 |
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| Confidence interval calculator | NIST/SEMATECH e-Handbook, 1.3.5.2 Confidence Limits for the Mean, NIST/SEMATECH e-Handbook, 7.1.4 What are confidence intervals?, NIST/SEMATECH e-Handbook, 7.2.4.1 Confidence intervals for a proportion, OpenStax Introductory Statistics 2e, 8.3 A Population Proportion, NIST/SEMATECH e-Handbook, 1.3.6.7.2 Critical Values of the Student’s t Distribution | October 28, 2026 |
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| Molarity calculator | OpenStax Chemistry 2e, 3.3 Molarity, OpenStax Chemistry 2e, 11.4 Colligative Properties, IUPAC CIAAW: Standard atomic weights | October 28, 2026 |
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| Dilution calculator | OpenStax Chemistry 2e, 3.3 Molarity | October 28, 2026 |
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| Significant figures calculator | OpenStax Chemistry 2e, 1.5 Measurement Uncertainty, Accuracy, and Precision | October 28, 2026 |
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Corrections
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