getassistancePercentage Increase / Decrease Calculator
Compare two values, change a number by a percentage, or work backwards to find the original value.
Your results
Enter an original and new value, then choose Calculate.
- Original Value
- New Value
- Difference
- Percentage Change
Results use the displayed values and are rounded to 2 decimal places where needed.
What is Percentage Change?
Percentage change shows how much a value increased or decreased relative to its original value. Sales rising from 1,000 to 1,250 have a difference of 250 and a 25% increase. A fall from 1,000 to 800 is a difference of 200 and a 20% decrease.
How to Calculate Percentage Increase
Percentage Increase = ((New Value − Original Value) ÷ Original Value) × 100
From 800 to 1,000, the difference is 200. Dividing 200 by 800 and multiplying by 100 gives a 25% increase.
How to Calculate Percentage Decrease
Percentage Decrease = ((Original Value − New Value) ÷ Original Value) × 100
From 1,000 to 750, the difference is 250. Dividing 250 by 1,000 and multiplying by 100 gives a 25% decrease.
How to Increase or Decrease a Number by a Percentage
Multiply the starting value by the percentage divided by 100 to find the change amount. Add it for an increase or subtract it for a decrease.
Change Amount = Starting Value × (Percentage ÷ 100)
An increase of 20% takes 1,000 to 1,200. A decrease of 20% takes 1,000 to 800.
How Reverse Percentage Works
To undo an increase, divide the final value by one plus the percentage as a decimal. To undo a decrease, divide by one minus the percentage as a decimal.
Before increase = Final Value ÷ (1 + Percentage ÷ 100)
Before decrease = Final Value ÷ (1 − Percentage ÷ 100)
For example, 1,200 after a 20% increase came from 1,000. A final 800 after a 20% decrease also came from 1,000. An original value cannot be recovered from a 100% decrease because every starting value becomes zero.
Percentage Change vs Percentage Points
If a rate rises from 20% to 25%, it rises by 5 percentage points. Relative to the original 20%, the percentage increase is 25%: (25 − 20) ÷ 20 × 100.
Why a 20% Increase Followed by a 20% Decrease Does Not Return to the Original Value
Starting at 1,000, a 20% increase gives 1,200. Decreasing 1,200 by 20% subtracts 240, leaving 960. The percentages use different base values, so equal increases and decreases do not cancel each other.
Worked Examples
| Original | New | Change |
|---|---|---|
| 100 | 110 | 10% Increase |
| 100 | 125 | 25% Increase |
| 100 | 150 | 50% Increase |
| 100 | 90 | 10% Decrease |
| 100 | 75 | 25% Decrease |
| 100 | 50 | 50% Decrease |
Frequently Asked Questions
How do I calculate percentage increase?
Subtract the original value from the new value, divide by the original, and multiply by 100.
How do I calculate percentage decrease?
Subtract the new value from the original, divide by the original, and multiply by 100.
What is the percentage increase from 100 to 120?
The difference is 20, which is 20% of the original 100, so the increase is 20%.
What is the percentage decrease from 100 to 80?
The difference is 20, which is 20% of the original 100, so the decrease is 20%.
How do I increase a number by 15%?
Multiply it by 1.15, or multiply by 15% and add that amount to the starting value.
How do I decrease a number by 15%?
Multiply it by 0.85, or find 15% of it and subtract that amount.
How do I find the original number before a percentage increase?
Divide the final value by one plus the percentage expressed as a decimal. After a 20% increase, divide by 1.20.
Is a 20% increase followed by a 20% decrease equal to zero change?
No. The decrease uses the increased value as its base. Starting at 1,000 produces 1,200 and then 960.
What is the difference between percentage change and percentage points?
Percentage points measure the direct difference between two rates. Percentage change compares that difference with the original rate.
Related Calculators
Profit Margin Calculator
See your profit or loss, margin and markup from a cost and selling price.
Open calculator ↗Markup Calculator
Calculate selling price, markup amount, profit and profit margin from your cost price.
Open calculator ↗Sales Tax / GST Calculator
Calculate Sales Tax or GST, add tax to a price or extract tax from a tax-inclusive amount.
Open calculator ↗Discount Calculator
Calculate sale prices, discount amounts, total savings, multiple discounts and original prices.
Open calculator ↗Profit & Loss Calculator
Calculate profit or loss, profit/loss percentage and profit margin from cost and selling price.
Open calculator ↗Commission Calculator
Calculate commission, commission percentage, original sales amount and base salary plus commission earnings.
Open calculator ↗Freelance Hourly Rate Calculator
Estimate a sustainable freelance hourly rate based on your income goal, expenses, working time and billable hours.
Open calculator ↗Calculating a Price Change?
Once your revised price is ready, use GetAssistance to create a quotation or prepare an invoice for your customer.