How We Build and Check Our Calculators

People use SenseCalc to make real decisions about their money, so accuracy comes first. This page explains how every calculator and guide is built, checked and kept up to date.

Where our numbers come from

We rely on primary, official sources wherever they exist:

• Federal taxes: IRS revenue procedures and newsroom releases (2026 brackets, standard deduction, credits and retirement plan limits).
• Payroll taxes: the Social Security Administration (wage base) and each state's labor or revenue department (disability insurance, paid family leave and similar programs).
• State income taxes: each state's revenue department, cross-checked against the Tax Foundation's annual state tax tables.
• Market rates: Freddie Mac's Primary Mortgage Market Survey, the Federal Reserve's G.19 consumer credit release, Experian auto-finance data and published savings and CD rate surveys.
• Consumer rules: the Consumer Financial Protection Bureau, the FDIC and federal law (for example, the Homeowners Protection Act for PMI cancellation).

Each calculator page lists its sources.

How calculators are tested

1. Formulas first. The math for each calculator is written as a separate, documented function that runs the same way everywhere.
2. Worked examples. Every function is tested against answers calculated by hand or with standard spreadsheet functions — for example, a $300,000 mortgage at 6.5% for 30 years must produce a $1,896.20 monthly payment.
3. Edge cases. We test zero interest, very short and very long terms, payments that don't cover interest, and income that crosses tax-bracket and wage-base limits.
4. Review before release. A calculator only goes live once all of its tests pass.

How we keep things current

• Tax figures are updated each year when the IRS and states publish new numbers, usually October through January.
• Starting interest rates are reviewed monthly.
• Mid-year law changes (like a state cutting its rate retroactively) are added as soon as they're confirmed by an official source.

Guides and articles

Our guides explain how the calculators work and answer common questions with worked examples. Writers use the same sources as the calculators, numbers in examples are recalculated before publishing, and every guide shows when it was last updated.

Independence

SenseCalc is supported by advertising. Advertisers have no influence over our calculators, results or guides, and we don't accept payment for coverage or placement.

Corrections

If you spot an error, please tell us through the contact page. We investigate every report, fix confirmed errors promptly and update the page's "last reviewed" date.