Percent means “per 100”
25% = 25/100 = 0.25 = 1/4. Convert to the form that makes the problem easiest.
CALCULATE · EXPLAIN · PRACTICE
Percentage Calculator
Enter any two parts of a percentage relationship and solve the third, then switch to change, difference, reverse percentage, percentage points, or batch mode.
9useful modes
exactrational core
localno account
PERCENTAGE TRIANGLE
Know any two. Solve the third.
PERCENT OF A NUMBER60
25% of 240 = 60
formula240 × 25/100
exact60
decimal60
COMMON PERCENT PROBLEMS
One workspace for the questions people actually ask
result92
80 × 1.15 = 92
percent change15%
(92 − 80) ÷ 80 × 100
percent difference22.2222%
|80 − 100| ÷ average(80,100) × 100
original100
85 ÷ 0.85 = 100
percentage points+5 pp
Relative change: +25%
combined percentage36%
40% × 90% = 36%
CONVERT
Percent ↔ decimal ↔ fraction ↔ ratio
decimal0.125
fraction1/8
ratio1 : 8
BATCH WORKSPACE
Apply one percentage to a whole list
Useful for prices, scores, budgets, or spreadsheet checks.
DAILY 12
Build percentage instincts
0 / 0best —
PERCENT OF
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Choose the best answer.
FOCUSED PRACTICE
Keep going without an account
0 / 0streak 0
MIXED
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Choose the best answer.
Part = percent × whole
Use part = whole × percent/100. Rearrange the same relationship to solve the missing percent or whole.
Change and difference are not the same
Percent change has an original baseline. Percent difference treats two values symmetrically and divides by their average magnitude.
Percentage points are absolute
A move from 20% to 25% is +5 percentage points but a +25% relative increase.
Methods, exactness & scope
Exact arithmetic first
Whole numbers, decimals, scientific notation, fractions and mixed numbers are parsed as exact rational values with JavaScript BigInt. Decimal display is rounded only for presentation.
Reverse calculations are explicit
A 15% decrease multiplies by 0.85, so reversing it divides by 0.85. This avoids the common mistake of simply adding 15% back.
Local learning product
The calculator, batch workspace, Daily 12 and practice run in your browser. No account, global rank, or server-backed history is implied.