Methodology
Where our numbers come from
Calculators that implement an official rule (a tax bracket, a contribution limit, a federal regulation) show the authority they were checked against and the date. Tools that are pure math, like a margin or a ratio, say that no governing authority applies. This page lists the references behind the calculator library, not a curated selection. Where a government body defines a figure, we use that body and nothing else.
- Organisations cited
- 116Organisations cited
- Government bodies
- 54Government bodies
- Individual citations
- 597Individual citations
- Source categories
- 8Source categories
Each calculator that implements an official rule shows its own source and the date it was checked. Corrections that change a result are listed on the changelog.
How we use these sources
Rules come from primary sources only
Anything that is legally defined — a tax bracket, a contribution limit, an RMD divisor, an insurance premium rate — comes from the body that sets it. No aggregator sits between us and the rule.
Defaults are starting points you can change
Current-condition figures — average mortgage rates, auto loan APR by credit tier, typical home values — come from market data publishers and load as editable defaults. They shape the first number you see, never the arithmetic.
A source without a working link is not a source
Our verification file forbids attaching an authority to a calculator without a checked URL. Tools whose maths is a standard accounting identity carry no citation at all rather than borrow one that does not apply.
The wider process — who reviews formulas, how corrections are handled, and what we will not publish — is set out in our editorial policy.
U.S. federal government and agencies
44 organisationsStatute, regulation, and official statistics. These are the bodies that actually set the numbers — tax brackets, contribution limits, benefit formulas, published rates. Where a federal source exists for a figure, we use it and nothing else.
Internal Revenue Service
irs.govFederal tax brackets and standard deductions (Rev. Proc. 2025-32, as amended by the One Big Beautiful Bill), retirement contribution and catch-up limits, Publication 590-A and 590-B for IRA contributions, distributions and the Uniform Lifetime and Single Life expectancy tables behind every RMD calculation, Publication 505 for withholding and estimated tax, Publication 936 for the mortgage interest deduction, Publication 969 for HSA rules, Publication 527 for rental property depreciation, Publication 575 for pension and annuity income, Topic 409 for capital gains treatment, Rev. Rul. 59-60 for closely held business valuation, and Fact Sheet FS-2008-25 on S corporation officer compensation.
113 references·TaxesRetirementReal estateInvestingBusiness
Consumer Financial Protection Bureau
consumerfinance.govAmortization methodology for every mortgage, auto and personal loan tool; the Regulation Z definition of APR that our fee-inclusive loan comparison solves for; credit card interest accrual and minimum-payment mechanics; HELOC draw and repayment period behaviour; the debt-to-income thresholds used in affordability tools; and the Loan Estimate structure our closing cost estimator mirrors.
85 references·MortgageLoansCredit cardsBudgeting
Cost-of-living adjustment history, the annual taxable wage base used in payroll and self-employment tax, full retirement age and early-claiming reduction factors, and the Office of the Chief Actuary Period Life Table that drives our annuity payout mortality model.
28 references·RetirementTaxesAnnuities
Federal Reserve Board
federalreserve.govH.15 Selected Interest Rates for CD and deposit rate defaults, the G.19 Consumer Credit release for average credit card APR, the Z.1 Financial Accounts for household balance sheet context, and the Survey of Consumer Finances, which supplies the net worth percentile benchmarks and the household balance-sheet comparisons.
22 references·LoansCredit cardsNet worthSavings
Bureau of Labor Statistics
bls.govCPI-U, U.S. city average, all items — the series behind every inflation adjustment, real-return calculation and historical purchasing power figure on the site. Consumer Expenditure Survey data backs the category benchmarks in budgeting tools, and Employer Costs for Employee Compensation supplies the benefit load percentages in the employee cost calculator.
21 references·InflationCost of livingBudgetingBusiness
7(a) loan structure and terms, and the small business financial management guidance behind our break-even, cash flow and employee cost tools.
14 references·Business
Federal Student Aid (U.S. Dept. of Education)
studentaid.govRepayment plan definitions and formulas — Standard, Graduated, Extended and the income-driven plans — plus consolidation rules and forgiveness eligibility criteria used across the student loan suite.
13 references·Student loans
FHA loan limits by county, upfront and annual mortgage insurance premium rates, and the FHA qualification ratios in our FHA calculator.
12 references·Mortgage
The investor bulletin on fees and expenses that underpins our expense-ratio drag modelling, and disclosure standards referenced in investment explainer content.
11 references·Investing
Fannie Mae
fanniemae.comSelling Guide underwriting standards — qualifying ratios, reserve requirements and rental income treatment — used in affordability, DSCR and house-hacking tools.
11 references·MortgageReal estate
Investor education material on compounding, fee impact and margin, referenced in investing explainer content.
8 references·InvestingRetirement
Federal Reserve Bank of St. Louis (FRED)
stlouisfed.orgCPIAUCSL for the inflation series and WPRIME for the prime rate, used as the machine-readable mirror of the primary BLS and Federal Reserve releases.
7 references·InflationLoansInvesting
VA loan entitlement rules and the funding fee schedule by service category, down payment and first-versus-subsequent use.
7 references·Mortgage
SEC Investor.gov
investor.govThe compound interest methodology our savings, SIP, dollar-cost-averaging and investment growth calculators are verified against.
6 references·InvestingSavings
Deposit insurance limits and national deposit rate context in CD and savings account content.
6 references·Savings
Freddie Mac
freddiemac.comThe Primary Mortgage Market Survey, which sets the 30-year and 15-year rate defaults shown when a mortgage calculator loads. Reviewed monthly.
5 references·Mortgage
U.S. Census Bureau
census.govAmerican Community Survey income and housing cost data used in the cost-of-living and affordability datasets.
4 references·Cost of livingNet worth
Federal Trade Commission
ftc.govCredit reporting rights and debt collection rules in credit-related explainer content.
3 references·CreditLoans
U.S. Dept. of the Treasury
treasury.govTreasury yield curve rates and federal tax administration references.
3 references·InvestingTaxes
TreasuryDirect
treasurydirect.govSavings bond and Treasury security terms, rates and redemption rules.
3 references·InvestingSavings
HealthCare.gov (CMS)
healthcare.govHigh-deductible health plan definitions that determine HSA eligibility.
3 references·RetirementBusiness
Federal Register
federalregister.govFinal rules and notices for figures published by regulation rather than in a guide.
3 references·TaxesStudent loans
U.S. Congress and Congressional Research Service
congress.govStatutory text and nonpartisan CRS analysis for recently changed tax and retirement law.
3 references·TaxesRetirement
Maximum monthly guarantee tables by age and annuity form, set annually under ERISA — the ceiling on what a terminated private pension can actually pay. Drives the pension value calculator.
2 references·Retirement
Federal Housing Finance Agency
fhfa.govAnnual conforming loan limits, including high-cost area limits.
2 references·Mortgage
Credit union share insurance limits and published loan rate comparisons.
2 references·SavingsLoans
U.S. Dept. of Labor
dol.govEmployer plan fiduciary rules and wage and hour standards in payroll cost tools.
2 references·RetirementBusiness
U.S. Dept. of Agriculture
usda.govRural Development loan eligibility and guarantee fees, and the Food Plans cost estimates used as grocery benchmarks.
2 references·MortgageBudgeting
AnnualCreditReport.com
annualcreditreport.comThe federally mandated free credit report service, referenced in credit improvement guidance.
2 references·Credit
The Comptroller's Handbook on commercial lending, which documents the 365/360 interest accrual convention used by banks — a method that produces more interest than a borrower usually expects and has been repeatedly litigated.
1 reference·LoansBusiness
Contribution limits, agency matching schedule and fund structure for the federal employee retirement plan.
1 reference·Retirement
FERS and CSRS annuity computation rules, creditable service definitions and eligibility ages for federal employees.
1 reference·Retirement
Fair Market Rents by metro area and county, published annually by law — the federal benchmark for what a standard-quality rental costs, used in rent increase analysis.
1 reference·Real estate
Bureau of Economic Analysis
bea.govRegional Price Parities by state and metro area — the index behind every city-to-city cost of living comparison.
1 reference·Cost of living
Federal Reserve Bank of New York
newyorkfed.orgHousehold Debt and Credit Report, used for balance and delinquency context.
1 reference·LoansCredit
Federal Reserve Bank of Minneapolis
minneapolisfed.orgThe long-run CPI series extending inflation comparisons back to 1800.
1 reference·Inflation
Medicare.gov
medicare.govPremium and enrolment rules in retirement healthcare cost estimates.
1 reference·Retirement
Federal poverty guidelines, used as thresholds in income-driven repayment calculations.
1 reference·Budgeting
Federal tax deposit scheduling referenced in quarterly estimated tax guidance.
1 reference·TaxesBusiness
Regulation text, including Regulation Z, where the exact wording governs a calculation.
1 reference·LoansTaxes
Cornell Legal Information Institute
law.cornell.eduAnnotated Internal Revenue Code sections where the statute itself is the clearest reference.
1 reference·Taxes
United States Courts
uscourts.govBankruptcy means test income standards in debt relief comparison content.
1 reference·Debt
The VIN decoder that reports final assembly plant — the test for whether a vehicle qualifies for the car loan interest deduction.
1 reference·Auto loans
National Futures Association
futures.orgRegistration and disclosure standards referenced in investment risk content.
1 reference·Investing
Canadian government and regulators
10 organisationsEquivalent authorities for our Canadian tools and the Canada affordability dataset — CRA rules, CMHC insurance premiums, Bank of Canada rates, Statistics Canada series.
Canada Revenue Agency federal and provincial tax brackets, RRSP and TFSA contribution room rules, CPP and OAS benefit formulas, and the Home Buyers' Plan withdrawal limits.
23 references·CanadaTaxesRetirement
Canada Mortgage and Housing Corporation
cmhc-schl.gc.caMortgage loan insurance premium rates by loan-to-value band, minimum down payment rules, and the amortization limits that constrain Canadian mortgage calculations.
7 references·CanadaMortgage
Financial Consumer Agency of Canada
fcac-acfc.gc.caCanadian mortgage payment mechanics, including the semi-annual compounding convention that makes Canadian amortization differ from U.S. amortization.
5 references·CanadaMortgageBudgeting
Bank of Canada
bankofcanada.caPolicy interest rate, the Canadian CPI series, and the inflation calculator baseline.
5 references·CanadaInflationMortgage
Statistics Canada
statcan.gc.caHousehold income, spending and shelter cost tables behind the Canadian provinces affordability dataset.
4 references·CanadaCost of living
Office of the Superintendent of Financial Institutions
osfi-bsif.gc.caGuideline B-20 residential mortgage underwriting, including the minimum qualifying rate — the Canadian mortgage stress test.
1 reference·CanadaMortgage
Revenu Québec
revenuquebec.caQuébec provincial tax brackets, which are administered separately from CRA.
1 reference·CanadaTaxes
Government of Ontario
ontario.caOntario land transfer tax rates and first-time buyer rebate thresholds.
1 reference·CanadaReal estate
Canada Border Services Agency
cbsa-asfc.gc.caDuty and import cost references in cross-border cost comparisons.
1 reference·Canada
City of Whitehorse
whitehorse.caMunicipal property tax mill rate for Yukon, where no territorial aggregate is published.
1 reference·CanadaReal estate
Professional bodies and standards setters
17 organisationsWhere no government body defines a method, the profession does. Accounting identities, valuation conventions, and appraisal standards come from the organisations that publish them.
Tax Foundation
taxfoundation.orgState-by-state income tax bracket compilations and effective property tax rates by county — figures each state publishes separately and no federal body aggregates.
6 references·TaxesReal estate
Financial Planning Association
financialplanningassociation.orgPractice standards referenced in retirement planning methodology.
3 references·Retirement
The AAII Journal publication of the Trinity Study — the withdrawal rate research our safe withdrawal rate, FIRE and retirement drawdown tools are verified against.
3 references·RetirementFIRE
Accounting Standards Codification definitions for revenue, EBITDA components and lease treatment in business valuation tools.
2 references·Business
Market Pulse survey multiples used as business valuation reference ranges.
2 references·Business
MLS Home Price Index benchmark prices by province.
2 references·CanadaReal estate
Streamlined Sales Tax Governing Board
streamlinedsalestax.orgThe multi-state rate and boundary tables maintained under the Streamlined Sales and Use Tax Agreement — the only body that publishes sales tax rates across member states in one place.
1 reference·Taxes
AICPA and CIMA
aicpa-cima.comValuation and attestation standards referenced in business tool methodology.
1 reference·BusinessTaxes
CFA Institute
cfainstitute.orgGlobal Investment Performance Standards for return calculation conventions.
1 reference·Investing
Appraisal Institute
appraisalinstitute.orgIncome capitalisation approach definitions behind cap rate methodology.
1 reference·Real estate
National Association of Realtors
nar.realtorExisting home sales and median price series for market context.
1 reference·Real estate
Property management fee conventions used as rental analysis defaults.
1 reference·Real estate
Construction cost breakdowns in build-versus-buy content.
1 reference·Real estate
Filing statistics and process detail in debt relief comparisons.
1 reference·Debt
Debt management plan structure and typical terms.
1 reference·Debt
Journal of Financial Planning (FPA)
onefpa.orgBengen's portfolio success rate research — the origin of the 4% rule and the basis for our withdrawal rate ranges.
1 reference·RetirementFIRE
Academic and research institutions
10 organisationsPeer-reviewed and institutional research behind the models that have no statutory definition — safe withdrawal rates, equity risk premiums, wealth distribution.
World Inequality Database
wid.worldGlobal wealth distribution percentiles behind the international net worth comparison.
4 references·Net worth
Equity risk premiums, industry cost of capital and EBITDA multiples by sector — the standard academic reference for valuation inputs.
3 references·InvestingBusiness
KFF
kff.orgEmployer health benefits survey premiums in retirement and employee cost estimates.
2 references·RetirementBusiness
Registered Statistics Canada data tables cited by permanent DOI.
1 reference·Cost of livingCanada
World Bank
worldbank.orgPurchasing power parity conversion factors for international comparisons.
1 reference·Cost of living
Residential property price statistics for cross-country housing context.
1 reference·Real estate
Tax Policy Center
taxpolicycenter.orgDistributional analysis of tax provisions in explainer content.
1 reference·Taxes
MeasuringWorth
measuringworth.comLong-run historical price and wage series for pre-1913 inflation comparisons.
1 reference·Inflation
Average student debt at graduation by state, used as calculator defaults.
1 reference·Student loans
Rich States, Poor States
richstatespoorstates.orgState tax burden rankings in relocation comparison content.
1 reference·Taxes
Financial institutions and asset managers
6 organisationsLong-run return series and annuity pricing published by firms with the data to produce them. Used for historical context and defaults, never for rules.
Vanguard
vanguard.comLong-run asset class return series and the portfolio allocation models referenced in stock-and-bond split guidance.
10 references·InvestingRetirement
Fidelity
fidelity.comS&P 500 historical average return series and retirement savings benchmark multiples.
6 references·InvestingRetirement
Morningstar
morningstar.comAnnual retirement income research updating safe withdrawal rate estimates against current valuations and yields.
6 references·RetirementFIRE
S&P Global
spglobal.comS&P 500 index history and the Case-Shiller Home Price Index.
4 references·InvestingReal estate
UBS
ubs.comGlobal Wealth Report distribution data for international net worth percentiles.
2 references·Net worth
ImmediateAnnuities.com
immediateannuities.comCurrent market annuity quotes, used to sanity-check our actuarial payout model against real pricing.
1 reference·Retirement
Market data and industry reports
18 organisationsCurrent-condition figures that no government publishes quickly enough — house price indices, average loan rates by credit tier, cap rate surveys. Used for defaults you can change, not for results.
Experian
experian.comState of the Automotive Finance Market — average auto loan APR by credit score band, and average balances by loan type. These set the rate defaults in auto tools.
9 references·Auto loansCredit
NerdWallet
nerdwallet.comAverage personal loan rate surveys by credit tier, used as calculator defaults.
6 references·Loans
Bankrate
bankrate.comAverage homeowners insurance premium by state in the affordability dataset.
4 references·Real estateInsurance
Zillow Research
zillow.comThe Zillow Home Value Index by state — the typical home value series behind the affordability index.
3 references·Real estate
CBRE
cbre.comUS Cap Rate Survey, used as the reference range in cap rate analysis.
2 references·Real estate
Edmunds
edmunds.comQuarterly average new and used vehicle transaction prices and loan terms.
2 references·Auto loans
WOWA
wowa.caAggregated Canadian land transfer tax and property tax rates by municipality, pending replacement with provincial primary sources.
2 references·CanadaReal estate
nesto
nesto.caCanadian property tax rate comparison by province, pending replacement with provincial primary sources.
2 references·CanadaReal estate
ATTOM Data
attomdata.comHome Flipping Report gross margin and holding period benchmarks.
1 reference·Real estate
multpl
multpl.comShiller CAPE ratio series for valuation context in return assumptions.
1 reference·Investing
Global Property Guide
globalpropertyguide.comGross rental yield benchmarks by country.
1 reference·Real estate
Mortgage Professional America
mpamag.comCanadian mortgage market rate reporting.
1 reference·CanadaMortgage
Independent finance publications
9 organisationsCited only where a practitioner published original analysis that became the reference implementation for a method. Never cited for a figure a primary source already carries.
Bogleheads
bogleheads.orgThe community wiki's documented three-fund and variable withdrawal methodologies, cited where it is the clearest public write-up of a method.
3 references·InvestingRetirement
Kitces.com
kitces.comMichael Kitces' original analysis on Roth conversion sequencing and withdrawal ordering — practitioner research with no primary-source equivalent.
2 references·RetirementTaxes
BiggerPockets
biggerpockets.comThe BRRRR method definition and standard operating expense assumptions.
2 references·Real estate
Early Retirement Now
earlyretirementnow.comThe Safe Withdrawal Rate Series — the most extensive public sequence-of-returns analysis, cited alongside the Trinity Study.
1 reference·FIRERetirement
Mr. Money Mustache
mrmoneymustache.comThe savings-rate-to-retirement-date relationship popularised in FIRE planning.
1 reference·FIRE
ChooseFI
choosefi.comCoast FIRE and Barista FIRE definitions as used in the FIRE calculator family.
1 reference·FIRE
Retirement Researcher
retirementresearcher.comWade Pfau's work on withdrawal strategies and annuity integration.
1 reference·Retirement
Investopedia
investopedia.comTerminology definitions in business valuation content.
1 reference·Business
The Motley Fool
fool.comHistorical market return context in investing explainer content.
1 reference·Investing
Live data services
2 organisationsFetched at request time rather than stored, so the figure you see is the figure published now. Exchange rates only.
ExchangeRate-API
er-api.comCurrent foreign exchange reference rates, fetched server-side at request time. Nothing is stored and no request is attributed to you.
1 reference·Currency
Frankfurter
frankfurter.appHistorical exchange rate series published by the European Central Bank, used for the currency trend chart.
1 reference·Currency
Found something wrong?
Tax law changes, agencies restructure their sites, and published rates move. If a figure here looks stale or a formula does not match the source it cites, tell us and we will check it against the primary document and correct it. Include the calculator name and the figure you are questioning.
Report a correctionOrganisation names are used to identify the sources of the data and methods behind our calculators. The identifying marks shown above are our own typographic labels, not the logos or seals of the organisations named. Listing a source does not imply that organisation endorses, sponsors, reviews or is affiliated with We Are Calculator. We Are Calculator provides estimates for informational purposes only and is not financial, tax or legal advice — see our disclaimer.