Math & Converters Calculators: Unit Converter Percentage Calculator

Percentage Calculator

Solve common percentage problems in seconds: find x% of a number, determine what percent one number is of another, or apply percent increase/decrease. Percent change between two values.

How this Percentage Calculator works

This tool covers four everyday percentage tasks. Enter your numbers, choose a mode, and we'll show the result and the key steps.

  • What is P% of A? Multiply A by P/100. Example: 15% of 200 = 200 x (15/100) = 30.
  • P is what percent of A? Divide P by A and multiply by 100. Example: 30 of 200 → (30/200) x 100 = 15%.
  • Increase/Decrease A by P% Multiply A by (1 ± P/100). Example: increase 250 by 12.5% → 250 x 1.125 = 281.25; decrease 250 by 12.5% → 250 x 0.875 = 218.75.
  • Percent change from A to B ((B - A) / A) x 100 shows the rise or drop in percent.

What is a percent?

A percent is a “per hundred” ratio. Writing 15% means 15 out of 100, or 15/100 = 0.15. Percentages make it easy to compare parts of different-sized totals.

Core percentage formulas

Task Formula Notes
Find P% of A A x (P / 100) “Percent-of” problem (e.g., tips, sales tax, discounts)
What percent is P of A? (P / A) x 100% Share or composition of a whole
Increase A by P% A x (1 + P / 100) Markup, growth, inflation
Decrease A by P% A x (1 - P / 100) Markdown, decline, depreciation
Percent change from A to B ((B - A) / A) x 100% Before/after comparison — use our

Percentage increase vs percentage points

Going from 10% to 12% is an increase of 2 percentage points, but a 20% relative increase (because 2 is 20% of 10). Percentage points compare two percentages directly; percent change compares their relative size.

Converting decimals and fractions

  • Decimal → Percent: multiply by 100 and add “%”. Example: 0.075 → 7.5%.
  • Percent → Decimal: divide by 100. Example: 7.5% → 0.075.
  • Fraction → Percent: divide numerator by denominator, then x100. Example: 3/8 = 0.375 → 37.5%.

Real-world uses

  • Shopping & pricing: discounts, sales tax, price markups/markdowns.
  • Personal finance: tips, interest, loan fees, savings growth.
  • Analytics & reports: KPIs, conversion rates, composition shares.
  • Everyday checks: invoice sanity-checks, quote comparisons, margin changes.

Tips & common mistakes

  • Don't mix up % change and percentage points.
  • For sequential changes, apply each step multiplicatively (e.g., -20% then +20% won't return to the start value).
  • Ensure the “whole” (A) isn't zero in “what percent?” and “percent change” problems.

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