F Test Calculator
Computes the F statistic as the larger sample variance divided by the smaller, along with the two degrees of freedom, for testing whether two variances are equal.
What this calculator does
The F Test Calculator estimates your result instantly from the values you enter, using standard statistics formulas. Computes the F statistic as the larger sample variance divided by the smaller, along with the two degrees of freedom, for testing whether two variances are equal. Calculations run in your browser, so nothing you type is sent to a server, and the output is an estimate rather than a certified or official figure.
Result
About F Test Calculator
This F test calculator forms the F statistic by dividing the larger of your two sample variances by the smaller, so the ratio is always at least 1. It also reports the numerator and denominator degrees of freedom, each equal to its sample size minus 1.
Use it to set up a test of whether two populations have equal variances, then compare the F value against a critical value from an F table.
Formula & Mathematical Calculation
F Statistic = f(Sample 1 variance, Sample 1 size, Sample 2 variance, Sample 2 size)
Calculated according to standard stats formulas implemented in the calculator core.
Calculation Example
With sample 1 variance 25 (size 12) and sample 2 variance 16 (size 15): F = 25 ÷ 16 = 1.5625. Because the larger variance is sample 1, df 1 = 12 − 1 = 11 and df 2 = 15 − 1 = 14.
Key Benefits
- Always places the larger variance on top so the F ratio is at least 1
- Reports both degrees of freedom automatically from the sample sizes
- Gives a ready statistic to compare against a critical F value
How to Use this Calculator
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Enter sample 1 variance and size
Type the first sample's variance and its number of observations (at least 2) into the Sample 1 fields. -
Enter sample 2 variance and size
Type the second sample's variance and observation count into the Sample 2 fields; the second variance must be greater than 0. -
Calculate
Select Calculate to see the F statistic and the two degrees of freedom, df 1 and df 2.
Assumptions & Limitations
What the calculation assumes
- Every value you enter is treated as an exact, known amount.
- Any rate or interval you enter is assumed to hold for the whole period unless the form asks for it separately.
- Results use standard published formulas and account only for the values entered above.
- Rounding is applied for display; the underlying calculation uses your full precision.
- Results are returned in the same units you enter, unless the tool states the output unit.
What it does not cover
- F Test Calculator produces a calculated result for reference and learning, not a certified or official measurement.
- Real-world outcomes differ when tolerances, rounding rules or local standards apply.
- Definitions and standards vary by region and change over time; verify the convention that applies to your case.
- Figures are only as accurate as the inputs you supply — check them before acting on the result.
- For work where the result carries real consequences, confirm it against an authoritative source.
Frequently Asked Questions
Free to use, no account needed. Calculations run in your browser, so nothing you type is sent to a server. Results are estimates — how we build and check our calculators.