Last reviewed: August 25, 2026
This page documents the shared rules behind Calcoras calculators. Individual tools may add more assumptions beside their results. Calculations run in your browser; the numbers you enter are not sent to Calcoras.
Paycheck and federal income tax
For 2026 estimates, we subtract the standard deduction ($16,100 for single filers and $32,200 for married filing jointly), then apply the seven progressive federal brackets to taxable income. The calculator adds employee Social Security tax at 6.2% up to the 2026 wage base of $184,500 and Medicare at 1.45%, plus the 0.9% Additional Medicare Tax above the applicable wage threshold.
- IRS: tax year 2026 inflation adjustments and brackets
- Social Security Administration: 2026 contribution and benefit base
State income-tax figures are simplified planning estimates. Many states use progressive brackets, credits, local taxes and special deductions that a single representative rate cannot reproduce. Do not use the state estimate to prepare a return.
Loans, mortgages and credit cards
Installment-loan tools use the standard amortization formula, converting annual percentage rate to a monthly rate and spreading principal plus interest over the selected number of payments. Unless a tool asks for them, results exclude lender fees, taxes, insurance, points and changing rates. Credit-card payoff projections apply monthly interest to the remaining balance and then subtract the chosen payment; a payment that does not exceed interest is flagged as non-amortizing.
Savings and retirement
Compound-growth tools convert the entered annual return to the selected compounding period, add contributions on the stated schedule and show nominal future dollars. Market returns and inflation are not guaranteed. Retirement withdrawals shown with a percentage rule are scenarios, not promises.
Testing and rounding
We test zero values, bracket boundaries, short and long terms, and representative examples after a formula change. Calculators keep full-precision values internally where practical and round only the displayed result, so a table may differ by a dollar from adding rounded cells.
Limitations and corrections
These tools are educational estimates and cannot model every contract, jurisdiction or household. Verify important decisions with the relevant institution or a qualified professional. To report a reproducible problem, send the URL, inputs and expected result to [email protected]. Our full review rules are in the Editorial Policy.