Math & Everyday Calculators
Percentage, GST, age, and discount calculators. Quick answers to the everyday maths problems everyone needs solved.
All Math Calculators
Why use Calculy for math calculations?
Every calculator on Calculy uses peer-reviewed formulas and updates in real time as you adjust inputs — no page reloads, no delays. Results are visualised with interactive charts so you can see not just the answer, but the full picture.
All calculations happen in your browser. No data is stored on our servers without your explicit consent. Used by 50,000+ people monthly for decisions that matter.
Frequently asked questions
How do I calculate a percentage?+
To find X% of Y: multiply Y by X and divide by 100. Example: 15% of 200 = 200 × 15 / 100 = 30. For percentage change: ((New − Old) / Old) × 100. The Percentage Calculator handles all four common percentage problems in one tool.
How do I add GST in Australia?+
To add 10% GST: multiply the ex-GST price by 1.10. Example: $250 × 1.10 = $275. To remove GST from an inclusive price: divide by 1.10. Example: $275 ÷ 1.10 = $250. The GST Calculator handles both instantly for Australia and 8 other countries.
How do I calculate a discount?+
Sale price = Original price × (1 − Discount/100). Example: 30% off $85 = $85 × 0.70 = $59.50. The Discount Calculator also shows total savings for multiple items and has a quick-reference grid for common discount percentages.
How is exact age calculated?+
Exact age is calculated by counting complete years, then remaining complete months, then remaining days — accounting for different month lengths and leap years. The Age Calculator also shows total days, weeks, hours, your birthday countdown, zodiac sign, and Chinese zodiac.