How our calculators work

The core formulas

Our calculators use the same time-value-of-money functions built into spreadsheets and used by lenders:

• Payment (PMT). The fixed periodic payment that amortizes a loan: Payment = P · r ÷ (1 − (1 + r)⁻ⁿ), where P is the principal, r the periodic interest rate (annual ÷ 12), and n the number of payments.
• Amortization. Each period we charge interest on the outstanding balance (balance · r), apply the rest of the payment to principal, and carry the new balance forward — producing the full schedule.
• Present & future value (PV / FV). Used for affordability, required-income and savings-style tools to solve for a loan amount or balance.
• Effective APR. Where fees or points are involved, we solve for the rate that equates the financed amount to the present value of the payments.

Assumptions we make

Unless a calculator asks for it, results assume a fixed interest rate, equal monthly payments, interest compounded monthly, and that extra payments are applied directly to principal. Property tax, insurance, PMI and HOA dues are included only where the tool provides fields for them. Adjustable-rate tools project future rates using the inputs you provide and cannot predict actual index movements.

What the results are — and aren't

Results are precise mathematical estimates, not quotes or approvals. Your actual loan terms depend on your lender, credit profile, local taxes and program rules that no general calculator can fully capture. We round displayed figures for readability while computing at full precision.

Keeping it current

We review default rates, contribution and loan limits, and tax thresholds periodically and update them as the market and rules change. Where a figure is time-sensitive (such as a contribution limit or typical rate), treat it as a starting point and confirm the current number with your lender.

Found an error?

We take accuracy seriously. If a result looks wrong, please tell us — we investigate every report and correct genuine errors promptly.