⚡ Quick answer
To calculate percent change, use the formula: ((new - old) ÷ old) × 100.
Percent Change Calculator
Compute relative percent change from an old value to a new value.
📖 What it is
The Percent Change Calculator helps you determine the relative change between an old value and a new value, providing insight into growth or decline. This tool is essential for anyone needing to assess performance metrics, price changes, or any scenario where comparison is critical.
To use the calculator, input the old value and the new value. The output will give you the percentage change, allowing you to see how much the new value has increased or decreased in relation to the old one.
It's important to note that the old value must be a non-zero figure to calculate percent change accurately. Additionally, be consistent with units used for both values to avoid errors in your results.
How to use
- Identify the old value and the new value.
- Subtract the old value from the new value.
- Divide the result by the old value.
- Multiply by 100 to convert it into a percentage.
📐 Formulas
- Percent Change Formula—((new − old) ÷ old) × 100
- Increase Calculation—(new - old) × 100 ÷ old
- Decrease Calculation—(old - new) × 100 ÷ old
💡 Example
To calculate the percent change from 80 to 100:
1. Subtract the old value from the new value: 100 - 80 = 20.
2. Divide the result by the old value: 20 ÷ 80 = 0.25.
3. Multiply by 100 to convert to a percentage: 0.25 × 100 = 25%.
Thus, the percent change is a 25% increase.
Real-life examples
Stock Price Increase
A stock price increases from $50 to $75. Percent change is ((75 - 50) ÷ 50) × 100 = 50% increase.
Sales Decline
A store’s sales drop from $200,000 to $150,000. Percent change is ((150,000 - 200,000) ÷ 200,000) × 100 = -25% decrease.
Scenario comparison
- Price Change: Increase vs Decrease—An item priced at $100 increases to $120 (20% increase) while another drops to $80 (20% decrease).
- Performance Metrics: Growth vs Decline—Company A's revenue grows from $1M to $1.2M (20% growth) compared to Company B's decline from $1M to $800K (20% decline).
Common use cases
- Evaluating sales performance over a quarter.
- Determining price changes in retail.
- Assessing investment growth over a year.
- Calculating changes in website traffic.
- Understanding cost increases in project budgeting.
How it works
The percent change is determined using the formula: ((new − old) ÷ old) × 100. This calculation effectively measures how much a value has increased or decreased based on a reference point, which is the old value. Remember, the old value cannot be zero, as it would render the calculation invalid.
What it checks
This tool checks the relative growth or decline between two measurements.
Signals & criteria
- Baseline
- Updated value
- Percent delta
Typical errors to avoid
- Using zero as the old value.
- Mixing units between old and new.
- Reporting absolute change as percent without dividing by baseline.
Decision guidance
Trust workflow
Recommended steps after getting a result:
- Input accurate old and new values.
- Ensure units are consistent between measurements.
- Double-check calculations for accuracy.
FAQ
FAQ
What if old value is zero?
Percent change from zero is undefined; use absolute change instead.
Are results signed?
Yes—negative means a decrease from old to new.