Utility Pages provides free online calculators for finance, health, design, and developer tools. Every calculator on this site uses peer-reviewed formulas and publicly-available reference data. This page documents what we use, why, and what you should keep in mind when relying on the outputs.
General principles
- Educational, not advice. All calculators provide estimates based on standard formulas. They are not financial, medical, legal, or tax advice. For binding decisions, consult a licensed professional.
- Privacy first.Calculations run client-side in your browser. Your inputs (income, weight, dates, etc.) are never sent to our servers, logged, or stored. You can verify by checking your browser's network tab while using any tool.
- Public data, public methods. Where calculators rely on external data (tax brackets, salary medians, cost-of-living indexes), we cite the source and publication year.
Data sources by topic
Federal taxes (income tax, FICA)
Federal income tax brackets are 2026 inflation-adjusted figures published by the IRS. We use the standard deduction ($15,000 single / $30,000 married filing jointly / $22,500 head of household) and apply progressive bracket math. FICA: Social Security 6.2% on wages up to the 2026 wage base ($168,600), Medicare 1.45% on all wages, plus 0.9% additional Medicare surcharge above $200K (single) or $250K (married).
Source: IRS Revenue Procedures, Social Security Administration. Updated annually after the IRS publishes the year's figures (typically November of the prior year). We do not model: alternative minimum tax (AMT), earned income tax credit (EITC), child tax credit, qualified dividends/capital gains rates, self-employment tax, or itemized deductions.
State taxes
State income tax rates and brackets sourced from each state's Department of Revenue / Department of Taxation publications for tax year 2026. Nine states have no state income tax: Alaska, Florida, Nevada, New Hampshire, South Dakota, Tennessee, Texas, Washington, Wyoming. Some states use flat rates; most use progressive brackets. Effective rates shown in our after-tax estimates use a simplified ~5% approximation for non-zero-tax states; for precise figures, use our state-specific Paycheck Calculator.
City local taxes
Local income tax rates sourced from each city's revenue/finance department. Notable rates: New York City 3.876% (graduated), Philadelphia 3.75% (resident wage tax), Detroit 2.4% (resident), Baltimore 3.20%, Columbus 2.5%, Pittsburgh 3% combined, Louisville 2.2%, Yonkers 1.6%. Rates updated when cities publish changes (typically annual). Some cities also have school-district taxes, occupational privilege taxes, or non-resident-specific rates which we don't model in the simple after-tax estimates.
Salaries by job and location
National median salaries by occupation are derived from the US Bureau of Labor Statistics Occupational Employment and Wage Statistics (OEWS) program, updated annually. State and city adjustments use cost-of-living multipliers based on the Bureau of Economic Analysis Regional Price Parities (RPP) program for state-level and major metro area indexes.
Important caveats: These are population medians. Real salaries vary ±30% by experience level (entry vs senior), employer (top-tier tech companies pay significantly above market for tech roles), specific metro area within a state, and specific role specialization. Treat our numbers as a starting reference; for negotiation or planning, cross-reference with Glassdoor, Levels.fyi, salary.com, or BLS state OEWS tables for your specific role.
Cost of living
City cost-of-living multipliers derived from BEA Regional Price Parities (most recent annual publication) plus adjustments for major metros within states (e.g., SF Bay Area separated from California state average). The index reflects average prices for a standard basket of goods and services — housing, food, transportation, healthcare, services. Component breakdowns (housing/food/transport indexes) are approximated from the overall index using research on relative cost-category sensitivity to local price levels.
For granular cost-of-living detail (rent by neighborhood, specific item prices), cross-reference with Numbeo, BestPlaces, RentCafe, or local real estate data.
Mortgages and loans
Standard amortization formula: payment = P × r / (1 − (1 + r)−n). PMI estimated at 0.5–1.5% annually based on credit score and down payment. State property tax rates from each state's tax assessor / department of revenue (most recent published). Homeowners insurance estimated as 0.4% of home value annually (national average; varies significantly by state and home age).
Health & fitness
BMI uses WHO classifications. TDEE uses Mifflin-St Jeor (1990) by default with standard activity multipliers (1.2–1.9). Body fat percentage uses US Navy circumference method or Deurenberg (BMI-based) formula. Pregnancy due date uses Naegele's rule (LMP + 280 days). Sleep cycle calculations use 90-minute average cycles. Heart rate zones use Tanaka (208 − 0.7×age), Haskell (220 − age), or Gulati (women-specific) formulas. None of these are medical advice — for personalized health decisions, consult a licensed healthcare provider.
Update frequency
- Federal tax brackets: updated annually (typically December) when IRS publishes the next year's inflation-adjusted figures.
- State tax rates: updated when states change rates (most stable year-to-year; major changes publicized).
- FICA wage base: updated annually when SSA publishes the new wage base (typically October).
- Salary medians: updated when BLS publishes new OEWS data (typically annual, mid-year for prior-year data).
- Cost-of-living multipliers: updated when BEA publishes new RPP data (typically annual, ~24-month lag from data year).
- Health formulas: stable — based on peer-reviewed publications. We update if new consensus formulas are published.
Limitations & disclaimers
This site provides educational estimates only. Specifically:
- Tax calculations simplify many real-world factors: filing status variations, dependents and credits, multi-state work, equity compensation (RSUs/stock options), self-employment, capital gains. For binding tax decisions, use FreeTaxUSA, TurboTax, or a CPA.
- Salary datareflects population medians, not personal targets. Always verify with multiple sources (Glassdoor, Levels.fyi, BLS OEWS) and your employer's actual pay scale.
- Mortgage and loan calculators show standard amortization. Your actual rate, fees, PMI, and approval depend on credit score, debt-to-income, and lender-specific underwriting.
- Health calculators (BMI, TDEE, BAC, pregnancy, ovulation) are educational. Talk to a licensed healthcare provider before making medical decisions.
- Legal calculators(BAC) are educational only — never use them to decide whether you're safe to drive.
- Cost-of-living estimates reflect averages. Actual costs vary by neighborhood, lifestyle, and family situation.
Privacy
Calculations happen in your browser using JavaScript. Your inputs are not sent to our servers. We do not log, store, or analyze user inputs. We use Google AdSense for ad revenue (which has its own data practices, disclosed in our privacy policy).
Corrections
Found an error in our data, formulas, or sources? Contact us and we'll review and update.
Last reviewed
This methodology page was last reviewed on April 28, 2026. Individual calculator data may be more recent — see each calculator's documentation for specifics.