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Our Methodology

How our calculators work.

LoanMathWorks uses established financial formulas and the information you enter to generate educational estimates for payments, interest, payoff timing, affordability and other common borrowing questions.

Our approach

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Use established financial formulas.
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Keep assumptions visible and understandable.
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Let you adjust inputs and compare scenarios.
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Clearly distinguish estimates from actual lender terms.
Our approach

Built around clarity and transparency

Financial calculators are most useful when you understand what goes into the result. We aim to keep the process straightforward.

1

Your inputs drive the result

Calculator results are based on the amounts, interest rates, terms, payments, fees and other assumptions you provide.

2

Standard formulas

We use commonly accepted mathematical formulas for amortizing loans, simple interest, compound interest and related calculations.

3

Educational estimates

Results are designed to help you understand and compare scenarios. They are not loan offers, approvals or guaranteed lender calculations.

The math

Common formulas used on LoanMathWorks

Different calculators use different formulas. These are some of the core calculations used throughout the site.

Amortizing Loan Payment

Used for many mortgage, auto loan and personal loan calculations.

M = P × [r(1+r)^n] ÷ [(1+r)^n − 1]

M = periodic payment, P = principal, r = periodic interest rate, and n = number of payments.

Simple Interest

Used when interest is calculated only on the original principal.

I = P × r × t

I = interest, P = principal, r = annual interest rate, and t = time expressed in years.

Compound Interest

Used when interest is added to the balance and can itself earn interest.

A = P(1 + r/n)^(nt)

A = ending amount, P = principal, r = annual interest rate, n = compounding periods per year, and t = years.

Debt-to-Income Ratio

Used to compare recurring monthly debt payments with gross monthly income.

DTI = Monthly Debt ÷ Gross Monthly Income × 100

The result is expressed as a percentage. Different lenders may classify debts or income differently.

Calculator assumptions

What may be included in a calculation?

Each calculator is designed for a specific purpose, so the exact inputs and assumptions vary from tool to tool.

When a calculator includes optional costs such as taxes, insurance, fees, extra payments or upfront charges, those amounts are only incorporated when the applicable inputs are provided.

The description on each calculator page explains what the tool is intended to estimate and which inputs are being used.

Loan amount: The principal amount entered by the user.
Interest rate: The annual rate entered into the calculator unless otherwise stated.
Loan term: The repayment period selected or entered by the user.
Extra payments: Included only in calculators that provide an extra-payment input.
Taxes, insurance and fees: Included only when the calculator specifically provides those inputs.
Understanding estimates

Why a lender's numbers may be different

LoanMathWorks calculators provide estimates based on the inputs and assumptions entered. Actual financial products may use additional information or different calculation methods.

Payment timing: Some lenders calculate interest using exact payment dates or daily accrual.
Fees and charges: Origination fees, closing costs and other charges may affect actual borrowing costs.
Taxes and insurance: Mortgage-related costs can vary by property, location, insurer and lender.
Rounding: Lenders may round balances, interest or payments differently.
Lender policies: Qualification standards, payment schedules and product terms vary by institution.
Precision & rounding

How results are displayed

Calculators may use greater numerical precision internally than the values displayed on the screen. Dollar amounts and percentages are generally rounded for readability.

Because payment schedules can contain many individual calculations, small rounding differences may accumulate over time. This is one reason a calculator estimate may differ slightly from a lender's official amortization schedule or payoff quote.

Using the results

Use calculators to explore scenarios

One of the most useful ways to use a financial calculator is to change one assumption at a time.

For example, you can compare a shorter loan term with a longer one, test a higher monthly payment, explore a different interest rate, or estimate how an extra payment might affect payoff timing.

These comparisons can help you understand how different variables affect the numbers before speaking with a lender or other financial professional.

Compare different interest rates.
Compare shorter and longer repayment terms.
Test the effect of extra payments.
Compare total interest and borrowing costs.
Review how balances change over time.

Put the numbers to work.

Explore LoanMathWorks calculators and adjust the inputs to compare different borrowing and repayment scenarios.

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