How to calculate percentage change

When a price moves from 200 to 250, the percentage calculator reports a 25% change. When you add 25% to 113, the result is 141.25. When you subtract 25% from 113, the result is 84.75. Those three modes cover “how much did it move?” and “what is the new price after a markup or discount?”

Three modes in this guide

For “what is X% of Y” without a before/after pair, use how to calculate percentages.

Method

Percent change:

change% = ((new − old) ÷ old) × 100

Add percent:

result = base × (1 + percent ÷ 100)

Subtract percent:

result = base × (1 − percent ÷ 100)

Old value cannot be zero in percent-change mode. The calculator rejects that case instead of returning infinity.

Worked examples

From 200 to 250

Using percent change with old 200 and new 250:

• Change = 250 − 200 = 50
• 50 ÷ 200 × 100 = 25%

That is a 25% increase. The same formula with a lower new value yields a negative percent (a decrease).

Add 25% to 113

Using add percent with percent 25 and base 113:

• 113 × (1 + 0.25) = 141.25

Subtract 25% from 113

Using subtract percent with the same inputs:

• 113 × (1 − 0.25) = 84.75

Microsoft’s Excel help walks similar increase and decrease examples with the same structure.

How to use the tool

1. Open the percentage calculator.
2. Choose Percent change, Add percent, or Subtract percent.
3. Enter the two numbers in the order the labels describe.
4. Read the result and the formula line.

These modes do not know about tax law, list-price rules, or rounding conventions on a receipt. They only apply the formulas above.

Reading the result without fooling yourself

A 25% rise from 200 to 250 is not “25 points.” Percentage points belong to comparing two percent rates (for example, 10% to 12%). Percent change always divides by the starting amount.

Discounts that stack (25% off, then another 10% off the reduced price) are not the same as a single 35% off the original. Run each step separately if that is how the seller applies them, or use one subtract-percent step if the offer is a single cut.

Markups work the same way in reverse: adding 25% to 113 lands on 141.25 in this tool. If a store “marks up” from cost with a different convention, confirm which base they use before you treat the calculator output as their shelf price.

When to use which mode

Use percent change when both the old and new amounts already exist (last month’s sales and this month’s, or two list prices). Use add percent when you start from one amount and a markup. Use subtract percent when you start from one amount and a discount. If you only know a percent and a base with no “before,” you want percent-of instead, covered in the percentages guide linked above.

Salary and price examples in teaching materials often use the same three shapes: change between two figures, increase by a percent, decrease by a percent. Lock your inputs to the same order the tool labels use so the formula line matches what you expect. If a spreadsheet shows a different rounded figure, check whether it used banker’s rounding or truncated intermediate steps; this tool’s library rounds to six decimals in the formula line for teaching clarity.

Try it

Run 200 → 250 on percent change, then 25% add and subtract on 113, and confirm 25%, 141.25, and 84.75.