# Subtracting Significant Figures (Sig Fig) Calculator

This Subtracting Significant Figures Calculator computes the subtraction of the numbers entered in and places the resultant value into proper significant figures.

Significant figures, or digits, are the values in a number that can be counted on to be accurate. Significant digits in a number are those values which can be known with certainty or a high degree of confidence, while insignificant digits are those which we do not trust as very accurate.

Significant digits are used extensively during measurements. Different measurement tools can record measurements of differing accuracy. Some measurement tools can record much more in detail than other measuring tools. For example, if we have a ruler that only measures centimeters, we can measure to one-hundredth of a meter. If we now change the ruler and get one which measures millimeters, we can measure to one-thousandth of a meter. Thus, we can have an extra significant digit, because the ruler is more detailed and allows for more accuracy of measurement.

It is important to be honest when making a measurement, so that the resulant value does not appear to be more accurate than the equipment used to make the measurement allows. And how we make the recorded value honest is by controlling the number of digits, or significant figures, used to report the measurement. The recorded value cannot have more significant digits than the measuring tool allows. This is why proper sig fig are important.

When subtracting significant digits, the amount of significant digits that will be in the final answer is determined by the number of significant digits present after the decimal place in the numbers we are subtracting. The final resultant value will have the same number of decimal place values as the subtrahend with the least amount of decimal places. Thus, if we have 254.6 minus 234.789 , the final resultant will have 1 decimal place, since one of the subtrahends only contains one decimal place. If any of the subtrahends have no decimal places, then the final subtraction resultant value will have no decimal places. If the subtrahend with the lowest amount of decimal places is 1, the final resultant will hold 1 decimal place. If the subtrahend with the lowest amount of decimal places is 2, the final resultant will hold 2 decimal places, and so on.

This is the only rule to follow when subtracting numbers and keeping proper significant figures.

To use this calculator, a user simply enters in the subtraction problem into the text box, and clicks the 'Calculate' buton. The resultant value in proper significant figures will be automatically computed and displayed.

Being that electronics, like any other science, deals with measurements, knowing how to subtract significant figures may be important. Depending
on the measuring tool in use determines how accurate it can measure. Using the proper number of
significant figures may be extremely important.

Examples

What is 237.65 - 12.2?

237.65 - 12.2= 225.4

Being that one of the subtrahends only has 1 decimal place, the final resultant value contains only one decimal place.

What is 131.256 - 78.12?

131.256 - 78.12= 53.13

Being that one of the subtrahends has only 2 decimal places, the final resultant value contains 2 decimal places.

What is 120 - 23.8?

120 - 23.8= 96

Being that one of the subtrahends has no decimal places, the final resultant value has no decimal places.

Related Resources

Adding Significant Figures (Sig Fig) Calculator

Multiplying Significant Figures Calculator

Dividing Significant Figures Calculator

Significant Figures (Sig Fig) Calculator

Significant Figures Rounding Calculator