How to Calculate Percentage Change?

What is percentage change?

Percentage change (or percent change) measures the difference in value using percentages.

How is percentage change used in Extension?

Percent change is one means of demonstrating program impact or conveying the magnitude of a change. It shows the difference between the after vs. before values. Percentage change can be positive or negative. Numbers (frequency counts) are typically used in the formula but percentages can be as well.

How do you calculate percentage change?

((after value – before value) / before value) * 100 = % change. Simply subtract the before value from the after value; then divide by the before value. Multiply the result by 100. Add a % sign and that is your percentage change.

How can I calculate a percentage change ?

To calculate a percentage change, you can use this formula: (((v2- v1))/ v1) * 100.

Calculating percentages using a calculator

Here is a warning about using the percentage button on a calculator: the result depends on when you press the % button in your calculation. Sometimes it has no effect, sometimes it seems to divide by 100, and at other times it multiplies by 100. Here are some examples

• Pressing 48÷400% gives an answer of 12. Now 48÷400 = 0.12, so pressing the % button has had the effect of multiplying by 100. This has found 48 as a percentage of 400.
• Pressing 1 ÷ 2 × 300% gives the answer 1.5. Now 1 ÷ 2 × 300 = 150, so pressing the % button here has divided by 100. This has found 300% of a half.
• Pressing 400 × 50% gives an answer of 200. Now 400 × 50 = 20, 000, so pressing % here has divided by 100. This has found 50% of 400.
• Pressing 50% × 400 results in 400 on the display, requiring = to be pressed to display an answer of 20,000. So pressing the % button here has had no effect.

Percentage Change Error

The percent error is used in many scientific applications. In labs, it measures how accurate an experiment is, compared to the expected (often numerical) outcome.

Calculating percentage change and expressing an increase or decrease. ( ΔV / |V1| ) * 100 = ((V2 - V1) / |V1|) * 100 = percentage change.