Calculator Methodology

Where A = final amount, P = principal, r = annual interest rate, n = compounding frequency per year, t = years, PMT = periodic contribution. This is the standard future value of a growing annuity formula.

Standard financial mathematics; verified against IRS Publication 550 and Investopedia compound interest methodology.

Assumes contributions are made at the end of each period. Does not account for taxes on interest earned.

Where M = monthly payment, P = principal loan amount, r = monthly interest rate (annual rate ÷ 12), n = total number of payments. This is the standard loan amortization formula.

Consumer Financial Protection Bureau (CFPB) mortgage calculation standards.

Assumes fixed interest rate and equal monthly payments. Does not include property taxes, insurance, or PMI in the base calculation (shown separately).

Future value of current savings plus future value of ongoing contributions. Withdrawal sustainability uses the 4% safe withdrawal rate (Bengen Rule) as a reference benchmark.

William Bengen's 1994 research on safe withdrawal rates; Vanguard retirement planning methodology.

Returns are nominal (before inflation). Real-world returns will vary. The 4% rule is a guideline, not a guarantee.

Assets include cash, investments, property, and other owned items of value. Liabilities include all debts and financial obligations.

Standard accounting definition; consistent with Federal Reserve Survey of Consumer Finances methodology.

Asset values are self-reported estimates. Market values fluctuate.

Calculates how much a sum of money today will be worth in the future, or what a future amount is worth in today's dollars.

Bureau of Labor Statistics (BLS) CPI methodology; Federal Reserve inflation calculation standards.

Uses a constant inflation rate. Actual inflation varies year to year.

Each portion of income is taxed at the rate for that bracket. The marginal rate applies only to income within that bracket, not to all income.

IRS Publication 505 (2024 tax year). Brackets updated annually.

Uses simplified 2024 federal brackets. Does not account for all deductions, credits, or state-specific rules.

A screening tool for weight categories. The WHO classification system is used: Underweight (<18.5), Normal (18.5–24.9), Overweight (25–29.9), Obese (≥30).

World Health Organization (WHO) BMI classification; CDC adult BMI calculator methodology.

BMI does not directly measure body fat and may not accurately reflect health for athletes, elderly individuals, or certain ethnic groups.

The Mifflin-St Jeor equation is considered the most accurate for most adults. W = weight in kg, H = height in cm, A = age in years.

Mifflin MD, et al. (1990). 'A new predictive equation for resting energy expenditure in healthy individuals.' American Journal of Clinical Nutrition.

Estimates resting energy expenditure. Actual BMR varies with body composition, health status, and genetics.

Activity multipliers: Sedentary (1.2), Light (1.375), Moderate (1.55), Active (1.725), Very Active (1.9). Based on the Harris-Benedict activity factor system.

Harris JA, Benedict FG (1918) with Mifflin-St Jeor BMR base; Academy of Nutrition and Dietetics guidelines.

Activity levels are self-reported. Actual energy expenditure varies with specific activities performed.

Uses circumference measurements to estimate body fat percentage. The Navy method is widely used for its accessibility (no equipment required).

Hodgdon JA, Beckett MB (1984). U.S. Navy body composition estimation method.

Circumference-based methods are less accurate than DEXA or hydrostatic weighing. Results are estimates.

The Devine formula is the most widely used clinical reference for ideal body weight. Results are shown alongside BMI-based healthy weight range for context.

Devine BJ (1974). 'Gentamicin therapy.' Drug Intelligence and Clinical Pharmacy.

Ideal weight formulas are clinical reference tools, not personal health targets. Individual healthy weight varies.

The contribution margin (price minus variable cost) represents how much each unit sold contributes toward covering fixed costs. Break-even is reached when total contribution equals total fixed costs.

Standard managerial accounting; consistent with AICPA cost accounting principles.

Assumes constant price and variable cost per unit. Does not account for economies of scale or price elasticity.

Simple ROI measures total return. Annualized ROI (CAGR) adjusts for time, allowing comparison across investments of different durations.

CFA Institute investment performance standards; standard financial analysis methodology.

Does not account for taxes, inflation, or risk. Past ROI does not predict future returns.

Gross margin measures profitability before operating expenses. Net margin measures profitability after all expenses. Operating margin falls between the two.

GAAP accounting standards; consistent with SEC financial reporting definitions.

Calculations use inputs as provided. Actual margin depends on accurate cost and revenue figures.