Percentage Change Calculator

Percentage change measures how much a value moved relative to where it started — the universal language of growth, inflation, markets, scores and improvement. The same 20-point swing reads as completely different percentages depending on the base, so this calculator exists to get the proportion right.

The formula

Percentage change = (new value − original value) ÷ original value × 100

Worked examples

From 80 to 100:

(100 − 80) ÷ 80 × 100 = 20 ÷ 80 × 100 = +25%

A 25% increase.

From 100 to 80:

(80 − 100) ÷ 100 × 100 = −20 ÷ 100 × 100 = −20%

A 20% decrease.

A positive result is an increase, a negative result a decrease, and the absolute-change output shows the raw size of the move (20 in both cases) alongside the proportion.

The famous asymmetry

A 25% rise from 80 lands on 100; a 25% fall from 100 lands on 75. Percentages always move against the current value, so gains and losses never simply cancel. An investment down 50% needs a 100% recovery — not 50% — to return to square one. That single fact is the most consequential thing about percentage change in personal finance: loss percentages and gain percentages are not mirrors of each other.

Why the base decides everything

A ₹10 rise is +10% from a ₹100 base but only +1% from a ₹1,000 base. A claim like "prices rose 25%" carries no usable meaning without its starting figure attached. When you quote a percentage change, always pair it with the base: "sales grew 25% from ₹4 lakh" is a complete statement; "grew 25%" alone is not.

Increase vs decrease: one formula, two signs

The formula does not care whether the move is up or down — the sign of the answer says so. That is why a single tool serves both questions, and why "percentage change" is normally reported with its direction: "traffic fell 8%", "scores improved 12%".

Reversing a change to recover the original

Given only the new value and the change percentage, the original is the new value divided by (1 + change ÷ 100). A price of ₹125 after a 25% increase was ₹125 ÷ 1.25 = ₹100; a price of ₹90 after a 10% cut was ₹90 ÷ 0.90 = ₹100. Whenever a percentage acts on an unknown base, the base is found by dividing, never by subtracting the percent — the habit that keeps spreadsheet formulas honest.

A caution on awkward bases

A starting value of zero makes percentage change undefined (division by zero), and negative bases twist the sign conventions into confusion. Tools like this expect the usual positive "from" value; for those edge cases, report the absolute change in units instead of a misleading percentage.

Real-world uses

• Finance — investment returns, index moves, exchange rates, inflation.
• Business — revenue growth, budget variance, cost overruns.
• Performance — marks, timings, distances — any "before and after" record.
• Population and economics — the quarterly growth rates economists and news outlets quote constantly.

Chained changes multiply, never add

For successive periods, multiply the ratios rather than adding the percentages. Prices up 10% then down 10% do not net to zero:

1.10 × 0.90 = 0.99  →  a net 1% loss

Compounding is why inflation, salary increases and market trends all need the multiply-not-add rule taken seriously.

Common mistakes

• Adding or subtracting percentages across different bases — the cardinal sin of percentage arithmetic.
• Dividing the change by the new value instead of the original.
• Using percentage change where a symmetric comparison is wanted — that is the percentage difference tool's job.
• Confusing percentage points with percent change: a lending rate rising from 10% to 12% is 2 percentage points but a 20% relative increase.

If you need to actually apply a percentage to a number — not compare two readings — use the percentage increase or percentage decrease calculators instead.