Calculator Methodology & Sources
Transparency is central to CalcFlo. Every calculator on this site is built on well-established formulas from peer-reviewed research, government agencies, and industry standards. This page documents the primary methodology and sources behind our most-used calculators.
Last reviewed: April 2026
Financial Calculators
Mortgage Calculator
Formula: Standard amortization formula — M = P × [r(1+r)n] / [(1+r)n − 1], where P = principal, r = monthly interest rate, n = total payments.
Sources:
- Consumer Financial Protection Bureau (CFPB) — Mortgage Key Terms
- Federal Reserve Board — Regulation Z (Truth in Lending)
Compound Interest Calculator
Formula: A = P(1 + r/n)nt + PMT × [((1 + r/n)nt − 1) / (r/n)], with optional regular contributions.
Sources:
- SEC Investor Education — Compound Interest
- Brealey, Myers & Allen — Principles of Corporate Finance (McGraw-Hill)
Retirement Calculator
Formula: Future value projections with inflation adjustment. Withdrawal analysis based on the 4% safe withdrawal rate.
Sources:
- Bengen, W.P. (1994). “Determining Withdrawal Rates Using Historical Data.” Journal of Financial Planning.
- Trinity Study (Cooley, Hubbard, Walz) — updated through 2020 data.
- Social Security Administration — Retirement Estimator methodology.
Loan & Debt Calculators
Formula: Loan calculators (auto, personal, student, EMI) use the same amortization formula as the mortgage calculator, adapted for different terms. Debt payoff calculators model minimum-payment snowball and avalanche strategies.
Sources:
- Federal Reserve — Consumer Credit G.19 Report
- CFPB — Paying Off Credit Card Debt
Health & Fitness Calculators
BMI Calculator
Formula: BMI = weight (kg) / height (m)2. Categories follow the WHO classification.
Sources:
- World Health Organization — BMI Classification (2000, updated 2023).
- CDC — About Adult BMI.
Calorie & BMR Calculator
Formula: Mifflin-St Jeor equation (1990). Males: 10×weight + 6.25×height − 5×age + 5. Females: 10×weight + 6.25×height − 5×age − 161. TDEE = BMR × activity factor.
Sources:
- Mifflin, M.D., et al. (1990). “A new predictive equation for resting energy expenditure in healthy individuals.” American Journal of Clinical Nutrition, 51(2), 241-247.
- Dietary Guidelines for Americans, 2020-2025 (USDA/HHS).
Body Fat Calculator
Formula: U.S. Navy circumference method. Males: 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76. Females include hip measurement.
Sources:
- Hodgdon, J.A. & Beckett, M.B. (1984). “Prediction of percent body fat for U.S. Navy men and women from body circumferences and height.” Naval Health Research Center Report No. 84-29.
- American Council on Exercise — Body Fat Percentage Chart.
Blood Pressure Calculator
Categories: Based on AHA/ACC 2017 guidelines.
Sources:
- Whelton, P.K., et al. (2018). “2017 ACC/AHA Guideline for Prevention, Detection, Evaluation, and Management of High Blood Pressure in Adults.” Hypertension, 71(6).
Math & Conversion Calculators
Percentage, Fraction, and Algebra Tools
Methods: Standard arithmetic operations and algebraic identities. Results are cross-verified against Wolfram Alpha and NIST reference data.
Unit Converters
Sources: NIST — Guide for the Use of the International System of Units (SI), SP 811. BIPM — SI Brochure (9th edition, 2019).
How to Cite a CalcFlo Calculator
If you reference CalcFlo in academic work, consumer education, or reporting, use the following formats:
APA 7th Edition
MLA 9th Edition
Chicago / Turabian
Replace [Calculator Name] with the tool’s title (e.g., “Mortgage Calculator”) and [page] with the URL slug.
Corrections & Feedback
If you believe any formula or source is incorrect, please contact us at admin@calcflo.com. We take accuracy seriously and will investigate all reports promptly.