Core percentage formulas
The calculators use standard arithmetic formulas and round results for readability.
part of whole: part ÷ whole × 100
percent of number: number × percent ÷ 100
percentage change: (new - old) ÷ old × 100
reverse increase: final ÷ (1 + percent/100)
reverse decrease: final ÷ (1 - percent/100)
Shopping and tax formulas
discount amount = original × discount% ÷ 100
sale price = original - discount amount
tax total = price × (1 + tax%/100)
net price = gross ÷ (1 + tax%/100)
Business formulas
markup% = (selling price - cost) ÷ cost × 100
margin% = (revenue - cost) ÷ revenue × 100
basis points = percentage × 100
Limitations
- Tax and VAT calculations are simple estimates and may not match local rules, exemptions, or rounding laws.
- Finance and business calculators do not replace accounting advice.
- Grade ranges are only rough examples and may not match your school scale.
- Displayed results may be rounded, while internal math uses the entered values.