FreeCalculators

Percentage Calculator

Find a percentage of a number, measure percent change between two values, or reverse-calculate the whole when you know the part and percent.

Planning & Life · Reviewed by FreeCalculators Editorial · Updated 2026-09-15

Your details

In 'of' mode: the number. In 'change': the starting value. In 'reverse': the part (result).

In 'of' mode: the percentage. In 'change': the ending value. In 'reverse': the percentage.

ShareWhatsAppXFacebookEmail

How it works

A percentage expresses a proportion out of 100. This calculator handles the three questions that cover most daily arithmetic: find X% of a number, measure percent change between two values, or reverse-calculate the whole when you know the part and the percent. Mode X% of a number multiplies: result = value × (percent ÷ 100). 15% of 200 = 200 × 0.15 = 30. Mode percent change compares two values: percent change = ((to − from) ÷ from) × 100, with absolute change = to − from. A value rising from 80 to 100 is a +25% change (absolute change +20) — not +20%, because the denominator is the starting value. Mode reverse answers X is Y% of what?: whole = part ÷ (percent ÷ 100). If 45 is 15% of a bill, the whole = 45 ÷ 0.15 = 300. The engine routes inputs A and B by mode — check the field hints when switching. Percent change is asymmetric: a drop from 100 to 80 is −20%, but recovering from 80 to 100 requires +25%, not +20%, because the base changed. For stacked discounts (25% then 10%), multiply surviving fractions (0.75 × 0.90 = 0.675), do not add percentages. This tool handles simple percentage arithmetic; compound growth over time belongs on the compound interest calculator.

Formula


                Mode: X% of a number
  result = value × (percent ÷ 100)
  Example: 15% of 200 = 200 × 0.15 = 30

Mode: percent change (from → to)
  % change = (to − from) ÷ from × 100
  Example: 80 → 100 = (100−80)/80 × 100 = +25%

Mode: reverse (X is Y% of what?)
  whole = part ÷ (percent ÷ 100)
  Example: 45 is 15% of ? → 45 ÷ 0.15 = 300

Tips

  • Percent change uses the starting value as the denominator — always label from and to clearly.
  • Stacked discounts multiply, they do not add — 20% + 10% off is 28% effective, not 30%.
  • Switch modes before entering values — field A and B mean different things in each mode.
  • To find what percent A is of B, compute A ÷ B × 100 or use reverse mode creatively.
  • A +25% recovery after a −20% drop still leaves you below the original — check the absolute numbers.

Frequently asked questions

How do I calculate 15% of 200?
Multiply 200 by 0.15 = **30**. In of mode enter value **200** and percent **15**; the result is **30**.
How do I find percent change from 80 to 100?
((100 − 80) ÷ 80) × 100 = **+25%**. Absolute change is **+20**. Select change mode with from=**80** and to=**100**.
45 is 15% of what number?
45 ÷ 0.15 = **300**. Use reverse mode: part=**45**, percent=**15**; the whole is **300**.
Why is a 20% drop and 20% gain not a wash?
Denominators differ. −20% from 100 lands at 80; +20% from 80 only reaches 96. Recovery requires **+25%** from the lower base — exactly what the 80→100 example shows.
Can this calculator do compound interest?
No — it handles simple percentage arithmetic in three modes. For growth on growth over time, use the [compound interest calculator](/en/tools/compound-interest-calculator).