Methodology & Data Sources

ClearFigure is built on a simple principle: every number we show you must be traceable to a published source. This page explains where our data comes from, how we verify it, and how we keep it current.

ClearFigure is an independent website and is not affiliated with any government agency.

Our Accuracy Standards

We only publish calculators where the formula is deterministic and verifiable against a primary source — an IRS publication, a mathematical law, or publicly available source data. We do not publish “estimate” tools where we can't show exactly how the answer was derived.

Every calculator on ClearFigure meets these requirements:

Cited source: The specific IRS publication, FRED series ID, or BLS series that provides the data is identified on every page.
Visible formula: The methodology section shows the exact mathematical formula used, with variable definitions.
Last updated date: Every page displays when the data was last verified or when the live API was last fetched.
Automated tests: Tax calculators are backed by a suite of hand-calculated test cases that verify the output against known-correct results. Currently 36 tests across federal income tax and self-employment tax.
Cross-validation: Federal tax brackets are verified across three independent sources: the IRS Revenue Procedure, PSLmodels/Tax-Calculator, and the Tax Foundation.

Data Sources

IRS Revenue Procedures

Federal income tax brackets, standard deductions, capital gains rates, and other tax parameters. Published annually by the Internal Revenue Service.

Examples:: Rev. Proc. 2025-32 (2026 brackets), Rev. Proc. 2024-40 (2025 brackets)
Update frequency:: Annual (published October/November for following tax year)
Used by:: Federal Income Tax Calculator, Self-Employment Tax Calculator

PSLmodels/Tax-Calculator

Open-source structured tax parameter data maintained by the Policy Simulation Library. Contains 200+ tax variables in machine-readable JSON, indexed by year. Used by academic researchers and policy analysts.

Examples:: policy_current_law.json — all federal tax parameters 2013–2035
Update frequency:: Updated within days of IRS Revenue Procedure publication
Used by:: Cross-validation of federal bracket data

Federal Reserve FRED API

Federal Reserve Economic Data — a comprehensive free source of U.S. economic data. Provides real-time financial rates sourced from institutions including Freddie Mac and the Federal Reserve.

Examples:: MORTGAGE30US (30-year mortgage rate), MORTGAGE15US (15-year), DGS10 (10-year Treasury yield)
Update frequency:: Mortgage rates: weekly (Thursday). Treasury yields: daily.
Used by:: Mortgage Calculator (live rates via ISR)

Bureau of Labor Statistics (BLS)

Published CPI-U (Consumer Price Index for All Urban Consumers) data used to measure inflation. Series CUUR0000SA0, not seasonally adjusted, base period 1982–84 = 100.

Examples:: Annual average CPI 1913–2025 (113 years of data)
Update frequency:: Monthly (annual averages used in our calculator)
Used by:: Inflation / Purchasing Power Calculator

U.S. Treasury Fiscal Data API

I Bond interest rates published by the Department of the Treasury. No authentication required. Returns fixed rate, inflation rate, and composite rate for all I Bonds since 1998.

Examples:: I Bonds Interest Rates dataset — semi-annual rate announcements
Update frequency:: Semi-annual (May 1 and November 1)
Used by:: I Bond Calculator (live rates via ISR)

Social Security Administration (SSA)

FICA tax rates and Social Security wage base published at ssa.gov. Wage base is updated annually; FICA rates have been unchanged since 1990.

Examples:: 2026 SS wage base: $184,500. FICA rates: 6.2% SS + 1.45% Medicare + 0.9% Additional Medicare.
Update frequency:: Annual (wage base). Rates unchanged since 1990.
Used by:: Self-Employment Tax Calculator, FICA calculation in state pages

Tax Foundation

Nonpartisan tax policy research organization. Publishes comprehensive state income tax bracket data annually with downloadable Excel files. Widely cited in academic and policy research.

Examples:: State Individual Income Tax Rates and Brackets, 2025 — all 50 states + DC
Update frequency:: Annual (published January/February for current year)
Used by:: All 51 state income tax calculator pages

Verification & Open Methodology

We publish machine-readable methodology artifacts and direct traceability links so you can independently verify our formulas, data sources, and implementation details.

Methodology version: 2026.02.14

Federal Income Tax Calculator

Progressive federal income tax with standard/itemized deduction handling.

Formula: Tax = sum over brackets of taxable amount in each bracket * bracket rate, after deductions.

Code references

Test references

Sources: IRS Revenue Procedures, PSLmodels Tax-Calculator

State and City Tax Add-ons

State and city tax logic layered on federal base for location-aware estimates.

Formula: Apply state and city brackets/flat rates to taxable base with local rules.

Code references

Test references

Sources: Tax Foundation

Self-Employment Tax Calculator

SE tax estimate using Social Security + Medicare rules.

Formula: SE Tax = SS component + Medicare component + additional Medicare over threshold.

Code references

Calculator function: src/lib/calculators/self-employment-tax.ts

Test references

Sources: IRS Revenue Procedures, Social Security Administration

Mortgage Payment Calculator

Fixed-rate amortization schedule and payment breakdown.

Formula: M = P * [r(1+r)^n] / [(1+r)^n - 1]

Code references

Test references

src/lib/calculators/__tests__/all-calculators.test.ts

Sources: Federal Reserve FRED API, Standard mathematical formulas

Compound Interest Calculator

Future value projection with recurring contributions and configurable compounding.

Formula: A = P(1 + r/n)^(nt) + PMT * [((1 + r/n)^(nt) - 1) / (r/n)]

Code references

Test references

src/lib/calculators/__tests__/all-calculators.test.ts

Sources: Standard mathematical formulas

401(k) Retirement Calculator

401(k) growth projection with contribution caps and employer match behavior.

Formula: Annual compounding with employee contribution + constrained employer match each year.

Code references

Calculator function: src/lib/calculators/retirement-401k.ts

Test references

src/lib/calculators/__tests__/all-calculators.test.ts

Sources: IRS Revenue Procedures, Standard mathematical formulas

Inflation Calculator

CPI-U based purchasing-power conversion between years.

Formula: AdjustedValue = Amount * (CPI_end / CPI_start)

Code references

Calculator function: src/lib/calculators/inflation.ts

Test references

src/lib/calculators/__tests__/all-calculators.test.ts

Sources: Bureau of Labor Statistics CPI-U

Profit Margin Calculator

Margin/markup relationships and target-price derivation.

Formula: Margin = (Revenue - Cost)/Revenue, Markup = (Revenue - Cost)/Cost, PriceFromMargin = Cost/(1-Margin).

Code references

Calculator function: src/lib/calculators/profit-margin.ts

Test references

src/lib/calculators/__tests__/all-calculators.test.ts

Sources: Standard mathematical formulas

Salary to Hourly Calculator

Converts annual salary and hourly wage under configurable weekly hours.

Formula: Hourly = Annual / (HoursPerWeek * 52), Annual = Hourly * HoursPerWeek * 52.

Code references

Calculator function: src/lib/calculators/salary-hourly.ts

Test references

src/lib/calculators/__tests__/all-calculators.test.ts

Sources: Standard mathematical formulas

Percentage Calculator

Percent-of, percent-change, and inverse percentage calculations.

Formula: PercentOf = Y * X/100, WhatPercent = X/Y * 100, PercentChange = (B-A)/A * 100.

Code references

Calculator functions: src/lib/calculators/percentage.ts

Test references

src/lib/calculators/__tests__/all-calculators.test.ts

Sources: Standard mathematical formulas

How We Keep Data Current

Different data types have different refresh cycles:

Data Type	Refresh Method	Frequency
Mortgage rates	Live from FRED API via ISR	Hourly
I Bond rates	Live from Treasury API via ISR	Daily
CPI / Inflation data	Embedded BLS data	Updated when BLS publishes annual average
Federal tax brackets	Manual update, 3-source cross-validation	Annual (when IRS publishes Rev. Proc., Oct/Nov)
State tax brackets	Manual update from Tax Foundation Excel	Annual (when Tax Foundation publishes, Jan/Feb)
SS wage base / FICA	Manual update from SSA	Annual

What Our Calculators Include and Exclude

We are transparent about the scope of each calculator. Tax calculators, for example, compute tax on ordinary income using standard deductions. They do not include:

Tax credits (Child Tax Credit, EITC, education credits, etc.)
Itemized deductions (mortgage interest, charitable giving, etc.)
Capital gains (taxed at different rates)
Other local income taxes (e.g. some OH/PA cities) — we include NYC when you select New York and opt in; data from Tax Foundation and published city/state sources
Pre-tax deductions (401k, HSA, etc.) unless explicitly entered

Each calculator's methodology section lists exactly what it includes and excludes. We prefer to be precise about a smaller scope than to be approximate about a broader one.

Found an Error?

If you find a discrepancy between our calculator output and the source data, we want to know. Please include:

Which calculator and what inputs you used
The result ClearFigure showed
What you believe the correct result is
The source you're comparing against (IRS publication number, URL, etc.)

We take accuracy reports seriously and will investigate and correct any verified errors promptly.

Disclaimer: ClearFigure provides calculators and tools for informational and educational purposes only. Results are estimates based on the information you provide and publicly available data. This is not tax, financial, legal, or investment advice. Consult a qualified professional for advice specific to your situation.

← Back to calculators