Methodology

The mortgage, PMI and FHA pages use the standard amortization formula: M = P × [r(1 + r)ⁿ] / [(1 + r)ⁿ − 1], where P is the principal, r the monthly interest rate (annual rate ÷ 12), and n the number of monthly payments. Each month, interest is charged on the outstanding balance and the remainder of the payment reduces the principal. Extra-payment scenarios are computed by continuing the same schedule with a larger payment until the balance reaches zero.

These pages show principal and interest only, except the FHA calculator, which adds mortgage insurance because the premium is mandatory on that loan type. Property tax, homeowners insurance, and HOA dues are not included on any page, because they vary by property and by contract rather than by loan terms.

The PMI calculator charges the annual PMI rate on the original loan balance, divided by twelve, and amortizes the loan to find the first month the balance reaches 78% of the original property value — the point at which cancellation is automatic. It also reports the earlier month at which the balance reaches 80%, when the borrower may ask for cancellation.

The FHA calculator applies the 1.75% upfront premium and an annual rate that depends on three things: the term, the loan-to-value ratio, and whether the loan is above the high-balance threshold. On a 30-year loan it is 0.5% up to 95% LTV and 0.55% above; a 15-year loan is priced at 0.15% or 0.4%. The annual premium runs for 11 years if the loan was at or below 90% LTV at origination, and for the full term above that.

The future value of an initial amount compounded monthly is FV = P × (1 + r/12)^(12t). With a monthly contribution of M added at the end of each month, the total is FV = P × (1 + r/12)^(12t) + M × [((1 + r/12)^(12t) − 1) / (r/12)]. Deposits are made at the end of each month, which is the more conservative of the two common conventions.

The savings goal calculator inverts the same formula, solving for the monthly deposit M that grows a current balance to a target over a given number of months.

The tax calculators use the 2026 federal income tax brackets for a single filer with the $16,100 standard deduction. Self-employment tax applies Social Security at 12.4% on net earnings up to the $184,500 annual wage base, and Medicare at 2.9% with no cap. Net earnings are net profit multiplied by the 92.35% exemption factor, which accounts for the half of the tax an employer would otherwise pay.

These are estimates for planning. They exclude state and local income tax, the additional Medicare surtax, above-the-line deductions other than the standard deduction, and tax credits such as the earned income tax credit or the child tax credit. For a filed return, use a tax professional or tax software.

We review these figures once a year, and out of cycle if the IRS publishes a change. The live configuration shows exactly what the site is using right now, and the health endpoint flags when the data has aged past its review date.

No calculator here accounts for inflation, currency changes, taxes on investment gains, employer-specific benefits, or the fee structures of any particular financial product. Where a rate or limit changes, we update the value and the date shown on the page.