BMI Calculator
Uses the standard BMI equation: weight in kilograms divided by height in meters squared, along with standard BMI category thresholds and a healthy BMI range for height-based weight estimates.
Methodology
How Calc Atlas calculators work
This page summarizes the formulas, assumptions, and calculation logic used across the site. The aim is not to turn every calculator into a math paper, but to make the core methods transparent enough that users can understand what a result is based on.
Health methodology
Calorie Needs Calculator
Uses the Mifflin-St Jeor equation to estimate basal metabolic rate and applies common activity multipliers to estimate maintenance calories, then adjusts targets for weight loss or gain.
Body Fat Calculator
Uses the U.S. Navy circumference method with the required body measurements for men and women.
Finance methodology
Compound Interest Calculator
Projects balance growth using recurring contributions, annual rate assumptions, and a selected compounding frequency based on standard future value math.
ROI Calculator
Calculates gain or loss relative to the initial amount invested, with annualized ROI used when a holding period is available.
Mortgage Calculator
Uses a standard amortizing loan formula for principal and interest, then layers in optional property tax, insurance, and HOA costs for a fuller monthly estimate.
Business and income methodology
Margin Calculator
Separates margin from markup so users can solve for price, cost, profit, or percentage inputs without mixing the two formulas.
Salary to Hourly Calculator
Converts annual salary and hourly pay based on hours per week and weeks worked per year, then layers in simplified tax and deduction assumptions for take-home pay estimates.
Everyday methodology
Percentage Calculator
Covers percentage of a number, what percent one number is of another, and percentage increase or decrease using standard percentage math.