Percentage Calculator

Formula

P% of V = (P/100)×V. Change = (New−Old)/|Old|×100. Difference = |A−B|/avg×100.

Reverse: Whole = Part ÷ (P/100). Add: V×(1+P/100). Subtract: V×(1−P/100).

How it works

Pick the question you are asking: what is P percent of V, what percent is A of B, what remains after adding or taking off P percent, or how far apart are two numbers. The engine normalizes every form to a fraction of a base, then scales by 100. Change uses the starting value as the base; symmetric difference uses the average so swapping A and B does not change the answer.

Assumptions

• Inputs are exact decimals; money answers round only at display.
• Change needs a non-zero starting value; a zero base has no meaningful percent change.
• Discounts compound multiplicatively (20% then 10% is 28% off, not 30%).

Default result

With Defaults: 10% of 100; change from 100 to 150 (per-mode defaults): 10% of 100 = 10 · change 100→150 = 50% increase

Worked examples

Tip and tax mental math

What is 15% of 200 (add-percent mode: 200 + 15%)

15% of 200 = 30 → total 230 — Example calculated with this calculator's formula.

Price change

From 100 to 125 (percent change mode)

100 → 125 = 25% increase — Example calculated with this calculator's formula.

Frequently asked questions

What is a percentage?

A percentage is a ratio expressed as a fraction of 100, marked with %. 45% means 45 per 100, or 0.45. The word comes from Latin per centum, "by a hundred."

How do I calculate P% of V?

Multiply V by P/100: (P/100) × V. So 10% of 100 = 0.10 × 100 = 10. Use the top panel for instant answers.

How do I find what percent one number is of another?

Divide and multiply by 100: (V1/V2) × 100. 25 is 12.5% of 200 because 25/200 × 100 = 12.5%.

If V is P%, what is the whole?

Divide by the rate: Whole = V / (P/100). If 25 is 20%, the whole is 25/0.20 = 125.