Skip to main content

    Data Accuracy & Formula Sources

    We take accuracy seriously. Every formula on CalcPlanet follows standard mathematical and scientific methods — and is tested against known results before deployment. →

    Finance Formulas

    Mortgage / Loan Amortization

    Standard amortization formula — M = P[r(1+r)^n]/[(1+r)^n−1]

    Compound Interest

    A = P(1 + r/n)^(nt) — NIST Handbook of Mathematical Functions

    Net Present Value (NPV)

    Standard discounted cash flow formula: NPV = Σ[Ct/(1+r)^t]

    IRR (Internal Rate of Return)

    Standard iterative root-finding on NPV=0 equation

    WACC

    Standard weighted average cost of capital formula from corporate finance

    Bond Yield (YTM)

    Standard yield-to-maturity formula based on present value of future cash flows

    Tax Brackets

    IRS Publication 15-T (2024 Federal Tax Tables)

    Health Formulas

    BMI (Body Mass Index)

    WHO – Body Mass Index Definition (2000). Weight(kg)/Height²(m²)

    BMR (Harris-Benedict Equation)

    Harris J, Benedict F. (1919). Carnegie Institute of Washington. Revised by Roza & Shizgal (1984).

    TDEE (Mifflin-St Jeor)

    Mifflin MD et al. (1990). J Am Diet Assoc. 90(3):286–90

    Body Fat % (Navy Method)

    Hodgdon & Beckett (1984). US Navy Physical Readiness Manual

    1-Rep Max

    Epley Formula (1985). National Strength and Conditioning Association

    VO₂ Max Estimation

    Rockport Walk Test — Kline et al. (1987). Medicine & Science in Sports & Exercise

    Target Heart Rate

    Karvonen Method (1957). American Heart Association guidelines

    Math & Science Formulas

    All mathematical formulas use standard methods consistent with academic references. Physics and chemistry formulas use SI units and constants from NIST CODATA 2018.

    Live Data Sources

    • Cryptocurrency prices: CoinGecko public API (updated every 60 seconds)
    • Currency exchange rates: Frankfurter API (European Central Bank data, updated daily)

    Our Testing Process

    • Source review — Check the documented formula and its assumptions against the cited reference
    • Calculation checks — Use deterministic examples to compare expected and computed results
    • Boundary checks — Existing tests exercise zero values, invalid inputs and selected extreme ranges; coverage varies by calculator
    • Reported errors — Reproduce discrepancies using the page URL, inputs and expected result, then check the method and source
    • Corrections — Add regression coverage where possible and record material published corrections; no response or resolution deadline is guaranteed

    Report an Error

    If you find a calculation discrepancy, please contact us with the calculator name, your inputs, and the expected result. →