The rule
Move the decimal point until exactly one non-zero digit sits before it. That gives a number from 1 up to (but not including) 10.
Count how many places you moved it: right for small numbers gives a negative power, left for large numbers gives a positive one.
Worked example
0.00042 becomes 4.2 x 10 to the power of -4, because the point moves four places right.
320,000,000 becomes 3.2 x 10 to the power of 8, because the point moves eight places left.
Standard form and scientific notation
The two names describe the same notation. UK exam boards and the GCSE syllabus say standard form; US courses say scientific notation.
The arithmetic is identical, so an answer written one way converts to the other without any change to the digits.
Inputs for the standard form calculator
Number to convert
Any number, large or small. The answer keeps one digit before the decimal point.
CALCULATOR QUESTIONS
Standard form calculator questions
What is 0.00042 in standard form?
4.2 x 10 to the power of -4. The decimal point moves four places right to leave 4.2.
What is 320,000,000 in standard form?
3.2 x 10 to the power of 8.
Is standard form the same as scientific notation?
Yes. UK schools say standard form and US schools say scientific notation for the same notation.
Can the coefficient be 10?
No. It must be at least 1 and less than 10, so 10 would be written as 1 x 10 to the power of 1 more.