Primary formula
n! = n x (n - 1) x ... x 2 x 1 for n greater than 1, with 0! = 1 and 1! = 1.
Math calculator
Factorial Calculator
Calculate n!, see the exact integer result where practical, and review digit count and trailing zeros.
Last reviewed: July 1, 2026Math advanced-number engine v1.0.0
Math calculator
Factorial Calculator
Calculations run locally from the values entered. Exact integer or rational output is labelled separately from decimal approximations.
Deterministic TypeScript
Calculate n! for a nonnegative integer.
Enter values and choose Calculate to show the result below the calculator.
Formula and assumptions
Input assumptions
n must be a nonnegative integer. 0! and 1! are both returned as 1. Trailing zeros are counted from factors of 5.
Precision note
Exact integer and rational results are labelled. Irrational roots, logarithms, and fractional powers are displayed as deterministic decimal approximations.
Advanced-number flow
Parse
Read decimal, scientific, fraction, or integer-list input from the original text.
Validate
Apply real-number and browser-safe integer range checks before calculating.
Calculate
Use deterministic TypeScript algorithms, Decimal.js, and BigInt where appropriate.
Label
Separate exact values, decimal approximations, tables, and warnings.
What the Factorial Calculator does
Factorial Calculator is built for calculating factorial products for nonnegative integers. It keeps the calculator at the top, then shows labelled exact values, approximations, steps, and method notes so the result is easy to audit.
How to use the Factorial Calculator
Choose the mode that matches the calculation, enter the requested values, and select Calculate. Reset returns the form to its default example values.
After a result appears, use Copy, Print, or Share to save the clean result summary without exposing hidden data.
Formula or algorithm
n! = n x (n - 1) x ... x 2 x 1 for n greater than 1, with 0! = 1 and 1! = 1.
Worked example
5! = 5 x 4 x 3 x 2 x 1 = 120.
Inputs and assumptions
The calculator parses text inputs first, then converts them to exact integer, rational, or Decimal.js values depending on the operation.
- n must be a nonnegative integer.
- 0! and 1! are both returned as 1.
- Trailing zeros are counted from factors of 5.
Exactness and approximations
Exact outputs are labelled as exact. Decimal outputs for irrational roots, logarithms, fractional exponents, and large scientific values are deterministic approximations rather than symbolic proofs.
The result card separates the headline value, supporting stats, step-by-step method, and warnings so rounded values are not confused with exact integer or rational results.
Visual result guide
The visual bar on the result card is a neutral magnitude snapshot. It does not classify a result as good, bad, high, or low; it simply helps scan the size of the calculated number.
Common mistakes
Most mistakes come from using the wrong operation, missing a domain restriction, or treating a rounded decimal as exact.
- Trying to use factorial for a negative integer.
- Using factorial notation on a decimal without a gamma-function context.
- Underestimating how quickly factorial values grow.
Limitations
This page is a practical calculator, not a computer algebra system. It does not attempt symbolic simplification for every possible expression.
- Large factorials are capped to keep the browser responsive.
- The calculator does not evaluate gamma-function extensions for non-integers.
Privacy and local calculation
The calculator works from the values you enter in the browser session. NexaCalc does not require accounts, databases, or paid external math APIs for these Math Phase 2 tools.
Educational disclaimer
This calculator is for general educational and practical checking use. Verify high-stakes academic, engineering, financial, or professional work independently.
Frequently asked questions
What does the Factorial Calculator do?
It helps with calculating factorial products for nonnegative integers. The calculator shows the main result, method, steps, and warnings where the mathematical domain has restrictions.
How does the Factorial Calculator calculate results?
n! = n x (n - 1) x ... x 2 x 1 for n greater than 1, with 0! = 1 and 1! = 1.
Are results exact?
Integer, rational, factor, GCD, LCM, and perfect-root results are exact where the tool labels them as exact. Irrational roots, logarithms, fractional powers, and very long decimal values are displayed as deterministic Decimal.js approximations.
Why are some inputs rejected?
The calculator rejects inputs outside the real-number domain, such as even roots of negative numbers or logarithms of nonpositive values. It also caps large integer searches so browser sessions stay responsive.
Can I enter scientific notation?
Yes. Decimal inputs such as 6.02e23 and 1.25e-4 are accepted by decimal-based tools, and rational tools parse scientific decimal text where exact conversion is practical.
Can I use negative numbers?
Yes when the operation is defined for negative values. The page shows validation messages for domains where negatives are not real-valued, such as logarithm arguments and even roots.
Do these calculators use an external math API?
No. Math Phase 2 calculators run from deterministic TypeScript logic in the app. No paid API, database, or external calculation service is used.
Are number-theory searches unlimited?
No. Prime checks and factorization are limited to practical exact ranges for a fast browser calculator. The page reports validation errors instead of attempting unbounded searches.
Are my inputs stored?
No. Inputs are calculated in the browser session and are not stored by NexaCalc.
What are the main limitations of the Factorial Calculator?
Large factorials are capped to keep the browser responsive. The calculator does not evaluate gamma-function extensions for non-integers.
References
- OpenStax Algebra and Trigonometry 2e, Section 6.1, Exponential Functions and exponent notation. Source.
- OpenStax Algebra and Trigonometry 2e, Section 6.3, Logarithmic Functions and change of base. Source.
- OpenStax Precalculus 2e, radicals and rational exponents review material. Source.
- OpenStax Prealgebra 2e, arithmetic foundations including factors, multiples, and integer operations. Source.
- decimal.js API documentation by MikeMcl, arbitrary-precision decimal arithmetic used for decimal approximations. Source.
- MDN Web Docs, BigInt reference for deterministic integer arithmetic in JavaScript. Source.
Math Phase 2 references and algorithm conventions reviewed on July 1, 2026.
Educational disclaimer
This calculator is for general educational and practical checking use. It is not a substitute for independent verification in high-stakes academic, engineering, financial, scientific, or professional work.
Rounded decimal results are approximations unless an exact integer, fraction, factorization, GCD, or LCM is explicitly shown.