Significant Digits

The significant digits of a number are those that contribute to its precision. All digits are significant except:
 * Placeholder zeros
 * Digits introduced after operations which result in an answer of greater precision than the original data

A simple rule for determining which digits are significant is to consider the number of digits required to represent that number in scientific notation. For example 1 130 000 has three signficant digits because it is rendered in scientific notation as 1.13 x 104.

Zeros

 * A zero before other numbers is never significant (e.g. 0054.7).
 * A zero between non-zero digits is always significant (e.g. 540.7)
 * A zero at the end of a number is significant if it is behind the decimal point (e.g. 54.70), but is not significant if it appears before the decimal (e.g. 5470)

Multiplication and division
The number of significant digits in a product or quotient should be rounded to the lowest amount of significant digits in the original data, avoiding any spurious precision implied by additional digits.

For example, the product of 0.023 x 365 = 8.395 is corrected to 8.4, rounding to the second significant digit since 0.023 only has two significant digits. Whole numbers like 365 have infinite significant digits.

Addition and subtraction
The number of significant digits in a sum or remainder should be restricted to the lowest amount of decimal places in the original data, not significant digits.

For example, in the following equation: 83.77 - 0.1075 = 83.6625, the answer is corrected to 83.66 since the lowest amount of decimal spaces in the original numbers is two.