Math Calculators
Percentage Change Calculator: Old vs New Value
Compare an original value with a new value to find relative change, direction, and absolute difference.
Enter the values and review the result.
The starting value or original amount.
The ending value after the change.
Calculation assumptions
- *Old value is used as the base for the percentage change.
- *Percentage change cannot be calculated when the original value is zero.
- *This calculator accepts a positive original value; negative starting values require a stated calculation convention.
- *A positive result means increase; a negative result means decrease.
Enter your values and press Calculate.
Results and breakdowns will appear here after a valid calculation.
What percentage change means
Percentage change compares a new value with a positive original value. Use it when you know both values and need the relative movement, its direction, and the absolute numerical difference.
Percentage change formula
Use percentage change = ((new value - old value) / old value) x 100. The result is positive for an increase and negative for a decrease.
Worked examples
Increase example: Old value 100 and new value 120 gives ((120 - 100) / 100) x 100 = 20% increase.
Decrease example: Old value 200 and new value 150 gives ((150 - 200) / 200) x 100 = -25%, or a 25% decrease.
When to use this specialist calculator
Use this calculator for before-and-after comparisons such as price changes, sales growth, website traffic, scores, budgets, or measurements. It always treats the original value as the base.
Use the Percentage Increase Calculator when you know a starting value and an increase rate, or the Percentage Decrease Calculator when applying a reduction rate. The general Percentage Calculator covers broader percentage questions such as finding a percentage of a number.
Common percentage change mistakes
- Using the new value as the base instead of the old value.
- Trying to calculate percentage change when the old value is zero.
- Confusing percentage change with percentage points.
- Ignoring whether the result is an increase or a decrease.
Related percentage tools
Learn the underlying concepts in Understanding Percentages, or browse Math Calculators for other focused workflows. Percentage-point change is different: moving from 20% to 30% is 10 percentage points, but a 50% relative increase.
Transparency note
Accuracy and limitations
Calzivo tools are built for practical estimates, conversions, and checks. Some tools use standard formulas or simplified assumptions, and results can be affected by input accuracy, rounding, units, local rules, or changing official requirements.
Results depend on the values you enter and any simplified assumptions used by the tool. Verify important results before making decisions or submitting official information.
How to Use This Tool
Use these steps to enter the right inputs and interpret the result correctly.
Enter the original or old value.
Enter the new value after the change.
Read the percentage change and the absolute difference.
Use the sign to tell whether the change is an increase or decrease.
Related Tools
Other helpful tools in the Math Calculators category.
Percentage Calculator
Calculate percent of a number, reverse percentages, known-rate adjustments, percentage change, and percentage difference.
Percentage Increase Calculator
Apply a known percentage increase to find the increase amount and final value.
Percentage Decrease Calculator
Apply a known percentage decrease to find the reduction amount and final value.
Scientific Calculator
Evaluate numerical expressions with powers, roots, logs, trigonometry, constants, and explicit degree or radian syntax.
Related Guides
Background reading and explanations related to Percentage Change Calculator: Old vs New Value.
Frequently Asked Questions
Common questions about Percentage Change Calculator: Old vs New Value and how to read the result.
How do I calculate percentage change?
Subtract the old value from the new value, divide by the old value, then multiply by 100.
What does a negative percentage change mean?
A negative result means the new value is lower than the old value, so the value decreased.
Why can't old value be zero?
The formula divides by the old value. Dividing by zero is undefined, so percentage change cannot be calculated from a zero starting point.
Can I use a negative original value?
Not in this calculator. Percentage change from a negative base can be defined in different ways, so this page requires a positive original value rather than presenting an ambiguous result.
Is percentage change the same as percentage difference?
No. Percentage change uses the old value as the base, while percentage difference usually compares two values relative to their average.
What is the difference between percent and percentage points?
Percent describes relative change. Percentage points describe the direct difference between two percentages, such as moving from 20% to 30%.