Calculator Methodology

BMI = weight (kg) / height² (m²); BMI = 703 × weight (lb) / height² (in²)

Sources: CDC Adult BMI · NHLBI Clinical Guidelines · WHO BMI classification

Mifflin-St Jeor (default), Harris-Benedict (revised 1984), Katch-McArdle (LBM-based)

Sources: Mifflin MD et al. (1990) Am J Clin Nutr · Roza & Shizgal (1984) · Academy of Nutrition and Dietetics

TDEE = BMR × Physical Activity Level (1.2 – 1.9) per WHO/FAO PAL system

Sources: USDA Dietary Guidelines 2020–2025 · WHO Energy & Protein Requirements · Academy of Nutrition and Dietetics

US Navy circumference method (Hodgdon & Beckett, 1984)

Sources: US Naval Health Research Center · ACSM body composition guidelines

Devine, Robinson, Miller, and Hamwi formulas — averaged across results

Sources: Devine BJ (1974) · Robinson JD et al. (1983) · Miller DR et al. (1983) · Hamwi GJ (1964)

90-minute sleep cycle model, plus 15-minute average fall-asleep latency

Sources: National Sleep Foundation · AASM clinical guidelines · Walker MP, Why We Sleep

Naegele's rule: LMP + 280 days (40 weeks); also supports conception date & ultrasound date methods

Sources: ACOG guidelines · Mayo Clinic · Pregnancy timeline studies

M = P × [r(1+r)^n] / [(1+r)^n − 1]; supports PMI, taxes, HOA

Sources: Federal Housing Finance Agency · Freddie Mac PMI guidelines · IRS Pub 936

Standard amortization (amortized), compound at-maturity (deferred), present value (bond)

Sources: CFPB lending guidelines · Federal Reserve loan data

Standard amortization with optional sales tax, fees, and trade-in equity

Sources: Edmunds True Cost to Own · FTC Auto Finance Guide

A = P(1 + r/n)^(nt); supports recurring contributions, inflation, and tax

Sources: SEC investor.gov · Federal Reserve SCF 2022 · BLS CPI · S&P Dow Jones Indices

SI = P × R × T / 100

Sources: Standard arithmetic; CFPB lending guidelines

Future value with annual contribution growth + 4% safe withdrawal rule

Sources: IRS 401(k) & IRA contribution limits · Trinity Study (Bengen 1994) · Vanguard research

FV = P × [((1 + r)^n − 1) / r] × (1 + r); supports stepped-up contributions

Sources: Standard SIP/DCA math; Vanguard 2012 DCA study

EMI = P × r × (1+r)^n / ((1+r)^n − 1)

Sources: Standard amortization math

Profit margin = (Selling Price − Cost) / Selling Price × 100; markup = (Selling − Cost) / Cost × 100

Sources: Standard retail accounting

Same as Loan Calculator; computes monthly payment given amount, rate, and term

Sources: Standard amortization math

% of X = (P / 100) × X; % change = (New − Old) / Old × 100; reverse % = Result / (P / 100)

Sources: Standard arithmetic

% = (Obtained / Total) × 100; supports subject-wise weighting and target marks projection

Sources: Standard grading math

Sale = Original × (1 − Discount/100); Discount % = (Original − Sale) / Original × 100

Sources: Standard retail math

Supports % off, stacked % discounts (sequential), flat coupons, BOGO/3-for-2/4-for-3 logic, tax, and shipping

Sources: NRF holiday shopping data · Adobe Analytics Cyber Week reports · CamelCamelCamel price history