How to Calculate Factorial: A Step-by-Step Guide
Calculates n factorial up to 170.
These calculations come up in school, at work and in daily life, from PSLE and O-Level practice to measuring a room for new flooring. Doing them by hand builds understanding, and a calculator lets you check the answer instantly.
What you need
- n
Step by step
- Enter the n.
- The results update as you type, or press Calculate.
- Read the n! first, then the supporting figures below it.
The formula
n! = 1 × 2 × … × n.
Worked example
For example, with these inputs:
- n: 10
the calculator returns:
- n!: 3,628,800
A second example
Now change the inputs to:
- n: 12.5
the calculator returns:
- n!: 479,001,600
Practical tips
- Keep units consistent: convert everything to the same unit before calculating.
- Write down the formula before plugging numbers in; it prevents mixing up variables.
- Use brackets to make the order of operations explicit.
- Estimate the answer roughly first so you can spot a result that is clearly wrong.
Background
Rounding is a common source of small errors. Keep full precision during intermediate steps and round only the final answer to the number of decimal places or significant figures the question asks for.
In everyday life the same maths shows up in discounts, recipe scaling, renovation measurements and comparing prices per unit. Being comfortable with it saves money and avoids costly measuring mistakes.
Each formula has assumptions built in. Area formulas assume flat shapes, volume formulas assume regular solids and statistical measures assume the data you enter is the data you want to describe. Knowing the assumptions helps you pick the right tool.
Related calculations
- Fraction Simplifier: Reduces a fraction to its lowest terms.
- Ratio Simplifier: Simplifies a ratio.
- Decimal to Fraction Converter: Converts a decimal to a fraction.
- Scientific Notation Converter: Writes a number in scientific notation.
Want to skip the arithmetic? The free Factorial Calculator does all of this instantly and updates as you type.
Run your own numbers: Factorial Calculator