Free Online Calculators
with Verified Formulas

Every calculator on Calculanum uses formulas verified against government and academic sources, with worked examples and full source citations.

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Popular Calculators

Compound Interest Calculator

Finance

Calculate how investments grow using compound interest. Formula: A = P(1 + r/n)^(nt).

Mortgage Calculator

Finance

Calculate monthly mortgage payments and see the full amortization schedule. Formula: M = P × r(1+r)^n / ((1+r)^n − 1).

BMI Calculator

Health

Calculate your Body Mass Index (BMI) in metric or imperial units. CDC standard categories: underweight, normal, overweight, and obese classes I–III.

BMR Calculator

Health

Calculate your Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE) using the Mifflin–St Jeor equation. Includes all 5 activity levels and Harris-Benedict comparison.

Percentage of Number Calculator

Percentages

Find a percentage of any number. Example: 10% of 200 = 20.

What Percent Of Calculator

Percentages

Find what percentage one number is of another. Example: 25 is 25% of 100.

Percentage Change Calculator

Percentages

Calculate percentage increase or decrease between two values.

Discount Calculator

Percentages

Calculate discounted prices and savings from a percentage discount.

Tip Calculator

Percentages

Calculate tip amounts and totals from bill amount and tip percentage.