Accuracy & Validation

Calculated vs. Estimated vs. User-Provided

To maintain transparency, the engine categorizes every number into one of three provenances:

• Calculated: Values produced by the model's formulas from selected settings and user-provided inputs, such as scheduled principal and interest.
• User-provided: Values you enter or select, such as loan amount, rate, country, or assumptions. MortMe does not independently verify them.
• Estimated: Values that depend on assumptions or incomplete external information, such as taxes, insurance, affordability capacity, or future-value scenarios.

Why Lender Figures Differ

Even when the model follows its stated formulas, its figures may differ from lender or servicer figures. In US covered transactions, a Loan Estimate is one example of a lender document; comparable documents and rules vary by jurisdiction. Reasons include:

• Payment Timing: Lenders may calculate interest using the dates between closing and the first payment.
• Tax and Insurance Escrow: Lenders often require you to prepay several months of taxes and insurance into an escrow account, changing your initial cash requirements.
• Rounding Rules: Different lenders may round partial pennies at different steps in the calculation pipeline.
• Changing Rates: Unless you have locked your rate, market interest rates fluctuate daily.

Our Testing Approach

MortMe uses decimal-based calculations and checks:

• zero-interest cases and final-balance reconciliation;
• payment schedules and extra payments;
• refinance comparisons and affordability calculations; and
• rate-change scenarios.

A check of the calculation logic cannot validate an individual lender's pricing, documents, timing, or underwriting. Results remain calculated outputs or estimates based on the inputs and assumptions provided.

For an applied estimate, use the mortgage calculator. Review the calculation methodology and sources and references to understand the assumptions behind the results.

MortMe is not a lender and does not determine loan approval or eligibility.