Percentage of a total
Part = total × percentage ÷ 100. Example: 15% of 250 = 37.5.
Part as a percentage
Percentage = part ÷ whole × 100. The whole must not be zero.
Reverse percentage
Whole = part ÷ (percentage ÷ 100). The percentage cannot be zero.
Percentage change
Change = (ending − starting) ÷ starting × 100. Use a positive, non-zero starting value for ordinary interpretation.
Weighted average
Weighted result = Σ(score × weight) ÷ Σ(weight). The weights must use a consistent unit and total more than zero.
Sequential discount
Final price = original × (1 − first discount) × (1 − second discount). A 20% discount followed by 10% is a 28% combined discount, not 30%.
Take-home pay scenario
Estimated net = gross pay × (1 − user-entered deduction rate) − other user-entered deductions. This is not an official tax calculation.
Compound-return illustration
Future value applies a user-entered annual rate compounded monthly to a starting amount and equal monthly contributions. It is an illustration, not a forecast.
Trade arithmetic
Long net = (exit − entry) × units − fees. Short net = (entry − exit) × units − fees. Real outcomes may differ because of costs and execution conditions.
Manual market-risk position size
Maximum instruments = floor(risk budget ÷ (price distance × multiplier × account-currency factor)). The multiplier and conversion factor are visitor inputs and must be verified for the particular share, forex pair, or futures contract.