Every step visible
Each calculator shows you exactly how the number was reached — formula, substitution, and result — so you can verify it yourself or hand it to someone who needs to check your work.
Built for the self-employed, contractors, and small business
Show your math.
Every calculator shows its work, cites its sources, and gives you a number you can send to your accountant.
244 free calculators for self-employment tax, quarterly estimates, contractor pricing, health, real estate, and more — plus 30 super calcs that chain them together, each with transparent step-by-step math.
Tax workflow
Don't guess which tax calculator comes next.
Start with the freelancer tax chain, then peel into quarterly estimates, safe harbor, and QBI with the same assumptions. One path, less retyping.
Step 01Full tax chainSE tax, federal brackets, state planning, retirement, and quarterlies.Step 02Quarterly estimateFederal quarterlies with SE tax, QBI, and deductions.Step 03Safe-harbor paymentFind the minimum quarterly target that avoids IRS underpayment penalties.Step 04QBI deductionModel the 20% pass-through deduction and high-income wage limits.
Housing workflow
Buying, refinancing, or investing? Start with the chained version.
ShowMath now groups the real-estate super calculators into one path: affordability first, refi breakeven second, investment-property returns third.
Affordability starts
Want the dashboard version?
Keep ShowMath for visible formulas, then jump to mitchreise.com for richer housing dashboards using matching starter assumptions.
Home affordabilityTurn the ShowMath housing result into a buyer-ready budget dashboard.Open dashboard Mortgage paymentStress-test payment, amortization, and rent-vs-buy from the hub.Open dashboard Refi breakevenCompare the refinance offer with payoff timing, fees, points, and savings.Open dashboard Rental ROIMove the investment scenario into cash flow, cap rate, and equity tracking.Open dashboard
Step 01 · Can I buy?Home affordability masterPreset: First-time buyerDTI, max responsible payment, mortgage amortization, rent-vs-buy crossover, and 30-year cost.Step 02 · Should I refinance?Mortgage refi enginePreset: Rate drop, long stayCurrent loan vs refi offer, financed fees, points, tax-shield delta, and breakeven month.Step 03 · Is this deal good?Real estate investment chainPreset: Cash-flow duplexCap rate, cash-on-cash return, mortgage payment, after-tax cash flow, and 5-year projection.
The differentiator
Super calculators that compose.
Every other calc site has 50 individual tools. ShowMath has the chained-context layer — fill your profile once and these super calcs combine 4–6 primitives into one end-to-end answer with every step visible.
- Contractor profit engineChains 5
- Complete fitness planChains 5
- Freelancer tax masterChains 4
- Wealth trajectoryChains 5
- Home affordability masterChains 5
- Real estate investment chainChains 4
Citations on every formula
IRS publications, state statutes, standard industry rates. Every number is sourced. You know where it comes from before you use it.
Free forever for core calcs
Self-employment tax, quarterly estimates, rate math, invoice pricing — the tools contractors and freelancers reach for most often cost nothing.
Most-used tools
The calcs contractors reach for most.
1099 Quarterly + SE Tax
SE tax + quarterly estimates
Quarterly Safe Harbor
Avoid the underpayment penalty
Freelance True Hourly Rate
W-2-equivalent contractor rate
Subcontractor Markup
Cost-plus markup math
Effective vs Marginal Tax Rate
Bracket-by-bracket federal tax math
Net Investment Income Tax
The 3.8% ACA surtax explained
Numbers you can stand behind.
Every calculator in the library shows its work. Cite it, screenshot it, send it. The math is documented so you don’t have to explain it.
Open the calculator library