Free Online Calculators
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A collection of free, browser-based calculation tools covering math, finance, physics, construction, health, computer science, and everyday life. Pick a calculator below or browse by category to find what you need.
Popular Calculators
Mortgage Calculator
Monthly principal and interest from price, down payment, rate and term — plus the lifetime interest the payment hides.
Compound Interest Calculator
Project growth from a starting balance and regular contributions, and see what starting ten years later actually costs.
ROI Calculator
Return on investment with proper annualization, so holding periods of different lengths become comparable.
BMI Calculator
Body mass index in metric or imperial units, with the WHO category ranges and where the measure misreads people.
Standard Deviation Calculator
Sample and population standard deviation worked step by step, including when to divide by n − 1 rather than n.
Quadratic Equation Solver
Solve ax² + bx + c = 0 for real or complex roots, with the discriminant explained before you compute anything.
Pythagorean Theorem Calculator
Find a hypotenuse or a missing leg, and use the 3-4-5 method to square a corner with nothing but a tape measure.
Ohm's Law Calculator
Voltage, current, resistance and power from any two values, with LED resistor and cable voltage-drop examples.
Concrete Volume Calculator
Cubic yards for slabs, footings and piers, including waste allowance and the bag count for a bagged pour.
Tip Calculator
Tip and per-person split, with mental-maths shortcuts and current tipping norms in the US and abroad.
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Featured Categories
Mathematics & Statistics
6 SUBCATEGORIES / 21 TOOLS
Physics & Engineering
5 SUBCATEGORIES / 18 TOOLS
Biology & Medicine
3 SUBCATEGORIES / 11 TOOLS
Finance & Economics
7 SUBCATEGORIES / 74 TOOLS
Computer Science & Data
4 SUBCATEGORIES / 13 TOOLS
Construction & Architecture
4 SUBCATEGORIES / 26 TOOLS