The basic formula for percentage change

Percentage change tells you how much something grew or shrank as a percentage of its starting value. In Excel, the formula is: (New Value − Old Value) / Old Value, then multiply by 100 to show it as a percentage.

If you sold 50 widgets last month and 75 this month, the percentage change is (75 − 50) / 50 × 100 = 50%. Excel does the math once you set up the cells correctly.

Key Takeaways

  • The percentage change formula is (New Value − Old Value) / Old Value, and you multiply by 100 to display it as a percentage.
  • In Excel, you can write this as =(B2-A2)/A2*100 if your old value is in A2 and new value is in B2.
  • Formatting a cell as a percentage automatically multiplies by 100, so you can skip the *100 step if you use percentage formatting.
  • Negative results mean the value decreased; positive results mean it increased.
  • You can copy the formula down to calculate percentage change for dozens of rows at once using the fill handle.

Setting up your data in columns

Start by putting your old values in one column and new values in another. For example, put last month's sales in column A and this month's sales in column B. Label the columns so you know what you are looking at — "Previous" in A1 and "Current" in B1 works well.

Your actual numbers go in row 2 and below. So if you have 50 in A2 and 75 in B2, you will write your formula in column C, starting in C2.

Writing the formula in a single cell

Click on cell C2 (or whichever cell you want the result in). Type: =(B2-A2)/A2*100

Press Enter. Excel calculates the result and shows it as a number — in this case, 50. That means a 50% increase.

If your result is negative, the value went down. For example, if A2 is 100 and B2 is 80, the formula gives you −20, meaning a 20% decrease.

Using percentage formatting instead of multiplying by 100

You can skip the *100 part of the formula if you format the cell as a percentage. Type =(B2-A2)/A2 instead, then press Enter.

Right-click the cell with your result. Choose "Format Cells". Click the "Number" tab, then select "Percentage" from the list on the left. Click OK. Excel automatically multiplies by 100 and adds the % symbol, so 0.5 becomes 50%.

This method is cleaner if you are working with many rows, because the formula is shorter and easier to read.

Copying the formula down to multiple rows

If you have 20 months of data, you do not need to type the formula 20 times. Click on the cell with your formula (C2). Look at the small square in the bottom-right corner of the cell — that is the fill handle. Click and drag it down to C21 (or however many rows you have).

Excel copies the formula and adjusts the cell references automatically. So C3 becomes =(B3-A3)/A3, C4 becomes =(B4-A4)/A4, and so on. Each row calculates its own percentage change.

If dragging feels awkward, double-click the fill handle instead. Excel fills down as far as it sees data in the adjacent columns.

Checking your work with a real example

Put these numbers in a test spreadsheet: A1 = "Old", B1 = "New", C1 = "% Change". Then A2 = 200, B2 = 250. In C2, type =(B2-A2)/A2*100 and press Enter. You should see 25, which is correct — 250 is 25% higher than 200.

Try another: A3 = 100, B3 = 60. The formula gives you −40, meaning a 40% decrease. That is also correct.

Once you see the pattern working, you can copy the formula to as many rows as you need and trust the results.

Common mistakes to avoid

The most common error is reversing the order — using (Old − New) instead of (New − Old). This flips your sign, so increases look like decreases. Check that you subtract the starting value from the ending value, not the other way around.

Another mistake is dividing by the new value instead of the old value. The percentage change is always relative to where you started, so the old value goes in the denominator. If you divide by the new value, your percentages will be wrong.

If you see #DIV/0! in a cell, it means you are dividing by zero — usually because the old value is 0. You cannot calculate percentage change from zero, so you will need to handle that row separately or leave it blank.

Frequently Asked Questions

What if my old value is zero?

You cannot calculate a true percentage change from zero because division by zero is undefined. Some people use a workaround like showing the new value as infinity or leaving the cell blank. The most honest approach is to note that the metric went from nothing to something, which is not a percentage — it is a new starting point.

How do I show percentage change as a decimal instead of a whole number?

Use the formula =(B2-A2)/A2 without the *100, and format the cell as a decimal with two decimal places. Right-click, choose "Format Cells", select "Number", and set decimal places to 2. A 50% increase shows as 0.50.

Can I calculate percentage change for negative numbers?

Yes, the formula works the same way. If you go from −50 to −30, the change is (−30 − (−50)) / −50 × 100 = 20 / −50 × 100 = −40%. The result is negative because you moved closer to zero, which is a decrease in absolute value.

What is the difference between percentage change and percentage point change?

Percentage change is what the formula calculates — the relative shift from old to new. Percentage point change is the straightforward difference: if something went from 40% to 45%, that is a 5 percentage point change, but a 12.5% percentage change. Use the formula for percentage change unless someone specifically asks for points.