How MyLoanCalcs.com Calculates Your Numbers
This page explains the formulas, assumptions, and data sources behind every calculator on MyLoanCalcs.com, so you can verify our results and understand their limits. Our aim is that any figure we display can be reproduced by hand or in a spreadsheet.
The Core Amortization Formula
Fixed-rate loan payments use the standard amortization formula: M = P[r(1+r)^n] / [(1+r)^n - 1], where M is the monthly payment, P is the principal, r is the monthly interest rate (the annual rate divided by 12), and n is the total number of monthly payments. This is the same formula published by the Consumer Financial Protection Bureau (CFPB) and used by mortgage servicers. Total interest is the sum of all payments minus the principal, and the amortization schedule splits each payment into interest (the outstanding balance times r) and principal (the remainder).
Methodology by Calculator
Mortgage, auto, personal, and student loan calculators apply the core formula above to the principal, rate, and term you enter, returning the monthly payment, total interest, and full amortization schedule.
The refinance and mortgage points calculators compute a break-even point -- the number of months for accumulated monthly savings to equal the upfront cost (closing costs or the price of points) -- by dividing the upfront cost by the monthly saving.
The bi-weekly payment calculator models 26 half-payments per year (equivalent to 13 monthly payments), applies the one extra annual payment to principal, and re-amortizes to find the shortened term and interest saved.
The debt consolidation and debt-payoff calculators compare the weighted-average rate of your existing balances against a single consolidation loan, and rank balances by rate (avalanche) or by size (snowball) to project payoff timelines.
Every calculator runs entirely in your browser using JavaScript. No inputs are transmitted to or stored on our servers.
Data Sources
Where we cite rates, limits, or fees, the figures come from official government and government-sponsored-enterprise publications: Freddie Mac's Primary Mortgage Market Survey (PMMS) for weekly rate data, the Federal Housing Finance Agency (FHFA) for conforming loan limits, HUD and the FHA for FHA loan limits, the U.S. Department of Veterans Affairs for VA funding-fee tables, and the CFPB for regulatory thresholds. We review these sources when the issuing agency updates them and note a "last updated" date on time-sensitive content.
Accuracy and Verification
Because our calculators use published, industry-standard formulas, you can verify any result independently -- by hand, in a spreadsheet, or against a lender's own calculator. Rounding in intermediate steps can cause small differences (typically a few cents) between our figures and a lender's, but the underlying method is identical. If you find a discrepancy, email us and we will investigate and correct it.
Limitations
Our calculators are educational tools, not loan offers or financial advice. They compute principal and interest and, where noted, specific add-ons; unless you enter them, they do not include property taxes, insurance, HOA dues, PMI, or lender-specific fees, so a real quote will differ. Adjustable-rate results are accurate only for the initial fixed period. For decisions specific to your situation, consult a licensed financial professional or a HUD-approved housing counselor.