How to Round to Significant Figures in Excel

To round to significant figures in Excel, you can use a combination of the ROUND and SIGNIFICANT functions. Here's a step-by-step guide on how to do this:

1. Open Excel and enter your data in a cell. For example, let's say you have the number 123.456 in cell A1 and you want to round it to 3 significant figures.
2. In another cell, let's say B1, type the following formula:

   =ROUND(A1, 3-1-INT(LOG10(ABS(A1))))

3. Press Enter, and you will see the rounded number in cell B1.

Here's a breakdown of the formula:

• LOG10(ABS(A1)) calculates the logarithm base 10 of the absolute value of the number in cell A1.
• INT(LOG10(ABS(A1))) returns the integer portion of the logarithm, which represents the number of digits before the decimal point.
• 3-1-INT(LOG10(ABS(A1))) calculates the number of decimal places to round to, based on the desired number of significant figures (3 in this case).
• ROUND(A1, 3-1-INT(LOG10(ABS(A1)))) rounds the number in cell A1 to the calculated number of decimal places.

Example

Let's say you have the following numbers in column A:

A
1  123.456
2  0.01234
3  56789

You want to round these numbers to 3 significant figures. In column B, you'll use the formula mentioned above:

B
1  =ROUND(A1, 3-1-INT(LOG10(ABS(A1))))
2  =ROUND(A2, 3-1-INT(LOG10(ABS(A2))))
3  =ROUND(A3, 3-1-INT(LOG10(ABS(A3))))

After entering the formulas, you'll get the following rounded numbers:

B
1  123
2  0.0123
3  56800

These numbers are now rounded to 3 significant figures.