The form
The standard form is a × 10n, where 1 ≤ a < 10 and n is a whole number. A positive exponent means a large number and a negative exponent means a small one. 320,000 is 3.2 × 105, and 0.00045 is 4.5 × 10−4.
E-notation
Calculators and code often write it as 3.2e5, where “e” stands for “times ten to the power of”. It has nothing to do with the constant e. The Scientific Notation Converter accepts either form.
Why use it
It keeps long numbers readable, shows the order of magnitude at a glance, and makes the number of significant figures explicit. Multiplication and division become simple: multiply or divide the front numbers and add or subtract the exponents.
Common misunderstanding
A number like 12 × 103 is not in standard form, because the front number is above 10; it should be 1.2 × 104. For a full guide, see how to convert numbers to scientific notation.