Retirement and tax, equity compensation, mortgages and real estate, health plans and vehicles. Each calculator states its formula, cites the rule behind it, and works through an example with real numbers.
Figures are taken from IRS, SSA, CFPB, EIA and other agency sources, with the date they were checked.
Backdoor Roth IRA pro-rata rules, Solo 401(k) vs SEP IRA limits, 401(k) employer match true-ups, HSA triple-tax growth, and 529 state tax benefits.
Mortgage extra principal vs S&P 500, loan recast vs refinance math, discount-point breakeven, home affordability, BRRRR underwriting, and rent-hike vs moving costs.
Startup ISO vs NSO stock options with Form 6251 AMT liability, RSU withholding shortfalls, Tech Offer total-comp comparison, W-2 vs 1099 vs C2C, and freelance rate pricing.
HDHP + HSA vs traditional PPO plan comparison with employer seed contributions, the HSA triple-tax deduction, and the long-run “stealth IRA” reimbursement strategy.
EV vs gas vs hybrid total cost, buying vs leasing, paying cash vs financing with 0% APR or a rebate, and repairing an older car vs replacing it.
Each runs in the browser and walks through its calculation step by step.
Splits a backdoor Roth conversion into its tax-free and taxable parts under the Form 8606 pro-rata rule.
Compares the cash and tax of exercising ISOs and NSOs, including the alternative minimum tax.
How a harvested loss offsets short- and long-term gains, the $3,000 ordinary-income limit, and what carries forward.
First-year Section 179 and bonus depreciation for business vehicles over 6,000 pounds GVWR, and the business-use test.
Capital left in the deal after a cash-out refinance, the loan payment, cash flow and coverage for a renovated rental.
The gap between 22% supplemental withholding and the federal tax a vest adds, and the Form 2210 penalty it can produce.
Employee and employer contributions per paycheck and per year, the contribution rate that reaches the full match, and vesting.
Calculate break-even timeline on 25bps–100bps rate cuts factoring closing points and amortized interest savings.
Weigh payroll premium savings and employer HSA seeds against deductibles and out-of-pocket maximums across three spending scenarios.
500 combinations of salary and ISO spread under 2025 AMT parameters: where AMT starts, and how the exemption phase-out raises the marginal AMT rate to 35%.
Browse every calculator in one place — retirement and tax planning, mortgages and real estate, startup equity and compensation, and health-plan comparison.
How the calculators are built, checked, and run without sending your inputs anywhere.
Every calculation occurs entirely within your browser's local memory using pure client-side JavaScript. When you calculate tax liability, debt amortization, or option spreads, your financial inputs never leave your browser.
Tax figures come from the published rules: the Internal Revenue Code (Sections 179, 1202, 415(c)), SECURE 2.0 distribution rules, and published IRS withholding tables. Each calculator links the source it relies on.
Every calculator is checked by an automated regression suite that re-runs its worked examples against standard financial formulas on each change, so published numbers stay reproducible.