Methodology

How these calculators work

Last reviewed: June 7, 2026

How we build a calculator

Each calculator on MortgageLab is built around a transparent formula and a documented set of inputs. The calculation runs entirely in your browser, so the figures you enter never leave your device. Where a result depends on published rates, tables, or thresholds, those values are stored in a single sourced data module rather than hard-coded in the interface.

Data sources and dating

Rates and reference values come from official primary sources — for example government agency publications — and each value is dated and cited in the underlying data module. When a calculator is tied to a specific year or data version, the page states which year or version it uses so you can confirm it matches your situation.

Estimates and limits

Results are estimates that apply common assumptions and do not model every individual case. Each calculator discloses the main simplifications it makes. Payments use standard fixed-rate amortization; the rate, taxes, and insurance you enter drive the estimate.

Corrections

If a value looks out of date or a result seems wrong, tell us through the contact page with the page URL and an official source, and we will review it.