How We Calculate
We believe a calculator is only as trustworthy as the method behind it. This page explains the formulas each CalcVue tool uses and the official sources our tax data comes from, so you can verify any result yourself.
Our principles
- Standard, verifiable formulas. Every calculation uses established financial mathematics — the same formulas used by lenders, accountants, and finance textbooks — not proprietary shortcuts.
- Official data, cited. Tax figures come directly from primary sources (the IRS and the Tax Foundation), never from estimates we invent.
- Estimates, not advice. Our tools are designed to inform a decision, not replace a professional. Every result page says so plainly.
- Calculations run in your browser. The numbers you enter are never sent to or stored on our servers.
Loan and mortgage payments
Mortgage, auto loan, student loan, and general loan payments use the standard amortization formula for a fixed-rate loan:
M = P · [ r(1 + r)ⁿ ] / [ (1 + r)ⁿ − 1 ]
where M is the monthly payment, P is the loan principal (price minus down payment), r is the monthly interest rate (the annual rate divided by 12), and n is the total number of monthly payments (years × 12). The amortization schedule is then built month by month: each payment is split into interest (the current balance × r) and principal (the remainder), and the balance is reduced until it reaches zero.
Compound interest, savings, and investments
Growth calculations use the compound interest formula with periodic contributions. A starting balance grows by A = P(1 + r/n)^(nt), and regular deposits are accumulated as a future-value-of-an-annuity series on top. You can change the compounding frequency and contribution amount in the compound interest calculator and watch how time and rate drive the outcome.
Federal and state income tax
Income tax is computed with progressive brackets: only the income that falls within each bracket is taxed at that bracket's rate, not your entire income. We apply the standard deduction for your filing status, then layer federal tax, FICA (Social Security and Medicare), and — where applicable — state income tax. Nine states have no wage income tax, and our tools reflect that.
Tax data sources and year
CalcVue's tax tools currently use 2026 tax-year data:
- Federal brackets & standard deductions — IRS Revenue Procedure 2025-32.
- Social Security wage base & FICA rates — Social Security Administration annual announcement.
- State income & sales tax rates — the Tax Foundation's 2026 state tax data.
We review these figures every year, typically between October and December, when the IRS, SSA, and state agencies publish updates. State bracket thresholds are inflation-adjusted and may vary by a small margin from individual state publications; we note this on each tax calculator.
Rounding and precision
Currency results are rounded to two decimal places and interest rates to four. Because intermediate steps keep full precision and are only rounded for display, a result may differ by a cent or two from a calculation done entirely by hand — this is normal and expected.
What our calculators do not include
To stay clear and broadly useful, our tools focus on the core calculation. They generally do not include items that vary widely by person or location — for example, property taxes, homeowners or PMI insurance, HOA dues, local city taxes, payroll deductions like 401(k) or health premiums, or one-off fees. Where these matter, we say so on the calculator and in its FAQ.
Found something wrong?
Accuracy matters to us. If you believe a formula or figure is off, please tell us — we investigate every report and correct genuine errors promptly.
This page is part of our commitment to transparency. CalcVue provides estimates for informational purposes only and is not financial, tax, or legal advice. See our editorial policy for how our content is produced and reviewed.