Calculating your new value is straightforward once you know the Percentage Increase Decrease formula and what each input means. This guide explains the method in plain language, walks through a manual calculation, and gives worked examples you can follow — then you can do it instantly with the Percentage Increase Decrease Calculator.
What is Percentage Increase Decrease?
The Percentage Increase Decrease calculation tells you your new value from a few simple inputs. The figure you are solving for here is the new value.
The Percentage Increase Decrease formula
The core formula is:
New value = Starting value + Change × Starting value × Percentage ÷ 100Here is what each input means:
- Starting value — a number. Example: 200.
- Percentage — a percentage, such as an annual rate. Example: 15%.
- Change — one of: Increase by, Decrease by. Example: Increase by.
How to calculate it step by step
- Write down the starting value (for example, 200).
- Write down the percentage (for example, 15%).
- Choose the change (for example, Increase by).
- Apply the formula above to get your new value.
- Double-check the result with the Percentage Increase Decrease Calculator.
Worked examples
Example 1
| Input / Output | Value |
|---|---|
| Starting value | 200 |
| Percentage | 15% |
| Change | Increase by |
| New value | 230.00 |
| Amount of change | 30.00 |
With starting value of 200, percentage of 15% and change of Increase by, the new value works out to 230.00.
Example 2
With starting value of 400, percentage of 15% and change of Increase by, the new value works out to 460.00.
| Result | Value |
|---|---|
| New value | 460.00 |
| Amount of change | 60.00 |
Example 3
With starting value of 100, percentage of 15% and change of Increase by, the new value works out to 115.00.
| Result | Value |
|---|---|
| New value | 115.00 |
| Amount of change | 15.00 |
Tips for an accurate result
- Keep your units consistent — mixing, say, months with years or grams with kilograms is the most common source of error.
- Round only at the very end. Rounding inputs early can shift the final answer noticeably.
- Re-run the numbers whenever an input changes, rather than estimating from an old result.
Prefer not to do the maths by hand? — the Percentage Increase Decrease Calculator does it instantly, for free, with the formula and a worked example built in.
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