How KalkWise calculators work
Every calculator on KalkWise uses standard, documented financial formulas. This page explains who maintains our tools, how we source our data, and how to report an error.
Last reviewed: October 2026
Who maintains KalkWise
KalkWise is independently built and maintained by its owner, Hen Machluf. Rules and rates come from official sources where we can use them — IRS revenue procedures and notices, SSA and CMS figures — and in some cases, such as combined state and local sales-tax rates, from the Tax Foundation. Our Data Sources page lists them. We are not CPAs or CFPs and do not provide personalized financial advice; for decisions that depend on your full situation, consult a licensed professional.
We update calculators whenever relevant regulations change (e.g., annual IRS tax-bracket adjustments, new contribution limits, updated state tax schedules).
Editorial standards
- ✓ Fixed test cases with hand-computed answers run before every deploy from our main branch. A change that moves a tested result fails the build.
- ✓ Regulatory inputs (tax rates, limits, thresholds) are refreshed each calendar year.
- ✓ We do not receive compensation from any financial institution for calculator results.
- ✓ Calculators are clearly labelled as estimates, not financial advice.
Methodology by category
Mortgage & Home
Amortization is computed using the standard annuity formula: M = P[r(1+r)^n]/[(1+r)^n−1], where P is principal, r is the monthly rate, and n is the number of payments. The interest rate is the one you enter.
Retirement & Investing
Future value projections use the compound-interest formula FV = PV × (1 + r)^n with optional periodic contributions. Contribution limits for 401(k), IRA, HSA, SEP IRA, and Solo 401(k) are updated annually from IRS notices. The 4% withdrawal rule references the Trinity Study (Cooley, Hubbard, Walz) updated methodology.
Tax
Federal income-tax brackets, standard deductions, and FICA rates are sourced from IRS Revenue Procedures and Publication 15. State income-tax rates are compiled from official state tax agency schedules. Self-employment tax calculations follow Schedule SE logic. Capital gains rates use IRS Tax Rate Schedules.
Loans & Debt
All loan calculators use the standard amortizing payment formula. APR-to-APY conversion uses the standard (1 + APR/n)^n − 1 formula. Debt payoff sequences (avalanche/snowball) are computed iteratively month by month, accounting for minimum payments and extra principal.
Savings & Inflation
Savings projections compound monthly. Inflation adjustments use the inflation rate you enter. I-Bond rates reference TreasuryDirect composite rate announcements.
Business & Advanced
NPV and IRR use standard discounted-cash-flow formulas; IRR is solved iteratively using Newton-Raphson. SaaS metrics (CAC, LTV, churn) follow widely accepted industry definitions. Payback period uses the simple undiscounted formula unless otherwise noted.
Primary data sources
Report an error
Found a formula error, a stale regulatory figure, or a calculation that doesn't match your expectations? We take accuracy seriously and aim to respond within 2 business days.
Email us at hello@kalkwise.com with the calculator name, the inputs you used, the result you received, and what you believe the correct result should be.
Disclaimer: KalkWise calculators are provided for general informational and educational purposes only and do not constitute financial, investment, tax, or legal advice. Results are estimates based on the figures you enter. Actual outcomes will vary. Consult a qualified professional before making financial decisions. Full disclaimer →