What is the Percentage Calculator?
Percentages appear everywhere — discounts, tax rates, interest, exam scores, growth numbers. The FinanceDeck Percentage Calculator handles the three most common percentage questions in one screen: what is X% of Y, and what percentage change is there between two values.
Even people comfortable with math sometimes fumble percentage change (up 200% vs. up to 200%). This tool removes the ambiguity by showing all three answers side by side.
How does it work?
For 'X% of Y', the calculator multiplies the two and divides by 100. For percentage change, it uses (New − Old) / Old × 100, which is negative for decreases. Both computations run in parallel, so you always see all outcomes at once.
Percentage change is asymmetric: going from 100 to 125 is a 25% rise, but going back from 125 to 100 is a 20% fall. This gotcha trips up many people; the calculator makes it obvious.
X% of Y = X × Y / 100; % change = (New − Old) / Old × 100Example
15% of 800 = 120. If 800 is your monthly grocery bill and you cut it by 15%, the new bill is ₹680.
A stock moves from ₹100 to ₹125 — that's a 25% rise. If it later falls back to ₹100, that's a 20% decline, not 25% — the base is different.
Benefits
- ✓Solves multiple percentage questions in one view
- ✓Handles negative changes correctly
- ✓Great for tax, discount and score math
- ✓No mental math or spreadsheet needed
- ✓Runs entirely in your browser
Frequently Asked Questions
Difference between percentage and percentage point?
10% to 12% is a 2 percentage-point increase but a 20% relative increase. Financial media often mix these up.
Can I compute reverse percentage?
Yes — swap the values. 'What is 20 as a percentage of 80?' equals 25%.
Is 100% increase the same as double?
Yes. A 100% rise means the new value is 2× the old value.
Percentage vs. basis points?
1 basis point = 0.01%. Bond yields and interest rates are quoted in bps for precision.
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