Round to the Nearest Thousandth – Online Calculator and Rules

Result of rounding the number to the nearest thousandth:

Round to Thousands

What Does It Mean to Round to the Nearest Thousandth?

Rounding a number to the nearest thousandth means simplifying the number by writing it with fewer significant digits while keeping its value close to what it originally was.

The rounded number is less precise (introducing some error), but easier to use in practice.

Most often, rounding a number to the nearest thousandth refers to mathematical rounding to the nearest thousandth part of the number.

Mathematical rounding to the nearest thousandth means rounding the number to three decimal places, where the difference between the original number and the rounded number is minimized.

Rounding Rules to the Nearest Thousandth:

  • The third digit after the decimal point (the thousandth part of the number) remains unchanged if the fourth digit after the decimal point is less than 5. (0; 1; 2; 3; 4)
  • The third digit after the decimal point increases by 1 if the fourth digit after the decimal point is 5 or greater. (5; 6; 7; 8; 9)

Examples:

  • 1.2221 rounds to 1.222 because the fourth digit after the decimal point (1) is less than 5
  • 1.2222 rounds to 1.222 because the fourth digit after the decimal point (2) is less than 5
  • 1.2223 rounds to 1.222 because the fourth digit after the decimal point (3) is less than 5
  • 1.2224 rounds to 1.222 because the fourth digit after the decimal point (4) is less than 5
  • 1.2225 rounds to 1.223 because the fourth digit after the decimal point (5) is equal to 5
  • 1.2226 rounds to 1.223 because the fourth digit after the decimal point (6) is greater than 5
  • 1.2227 rounds to 1.223 because the fourth digit after the decimal point (7) is greater than 5
  • 1.2228 rounds to 1.223 because the fourth digit after the decimal point (8) is greater than 5
  • 1.2229 rounds to 1.223 because the fourth digit after the decimal point (9) is greater than 5
  • 3.141 rounds to 3.14 because the fourth digit after the decimal point (1) is less than 5
  • 1.5549 rounds to 1.55 because the fourth digit after the decimal point (4) is less than 5
  • 1.555001 rounds to 1.56 because the fourth digit after the decimal point (5) is equal to 5