10/1 ARM Calculator — 10 Years Fixed, Then Adjustable

A 10/1 ARM is a hybrid adjustable-rate mortgage: the interest rate is fixed for the first 10 years, then adjusts once per year for the remaining loan term (typically 20 more years on a 30-year loan). The "10" is the fixed-rate period in years; the "1" means the rate can adjust every 1 year after that. This calculator shows your fixed-period payment, your remaining balance at reset, and your new payment at the assumed post-reset rate. Estimates only — not financial advice.

For a 10/1 ARM, after 10 years what happens is simple: after 120 fixed payments, your lender recalculates your monthly payment using the remaining balance, the remaining loan term, and the new rate (index + margin, subject to caps). Your payment can go up or down each year after that. This calculator re-amortizes the remaining balance over the remaining months at your assumed reset rate, which is the standard industry method.

Three steps: (1) compute the remaining balance after 120 payments with the standard amortization formula B = P(1+r)^k − M·((1+r)^k − 1)/r; (2) determine the reset rate = index + margin, limited by the first-adjustment cap; (3) re-amortize that balance over the remaining months at the reset rate using M = P·r(1+r)^n/((1+r)^n − 1). This page does all three automatically.

Payment shock is the jump in your monthly payment when the fixed period ends and the rate resets higher. For example, a $400,000 loan at 6.00% pays $2,398/month for 10 years; if the rate resets to 7.50%, the payment rises to about $2,697/month — a $298 (12.4%) increase. This calculator shows the dollar and percentage shock so you can plan for it. Not financial advice.

Caps limit how much your rate can rise and are usually quoted as three numbers, e.g. 2/1/5: the first adjustment can add at most 2 percentage points, each later annual adjustment at most 1 point, and the rate can never exceed the initial rate + 5 points (the lifetime cap) over the life of the loan. This calculator applies the first-adjustment cap to your assumed reset rate and shows a worst-case payment at the lifetime cap.

The 10/1 ARM index margin explained in one line: fully indexed rate = index + margin. The fully indexed rate is the rate your loan would reset to without caps: a published index (such as SOFR) plus the lender's margin stated in your note (for example, index 4.25% + margin 2.75% = 7.00% fully indexed). Enter your best estimate of this rate as the "assumed rate after reset" above. Your actual reset rate comes from your loan disclosure — this is an estimate, not financial advice.

It depends on your plans. A 10/1 ARM usually starts with a lower rate than a 30-year fixed, so you pay less interest if you sell or refinance within 10 years. A 30-year fixed costs more upfront but your payment never changes. Compare the total interest in both scenarios above — and remember this calculator assumes the reset rate stays flat after year 10, which is a simplification. Not financial advice; talk to a licensed mortgage professional. 10/1 ARM vs fixed-rate mortgage pros and cons in brief: the ARM offers a lower starting rate and 10 years of payment certainty (pros) but exposes you to payment shock and reset risk afterward (cons).

Only the length of the initial fixed-rate period: 10, 7, or 5 years. Shorter fixed periods usually offer lower starting rates but expose you to rate resets sooner. After the fixed period, all three typically adjust annually (the "/1"). A 10/1 ARM suits borrowers fairly confident they will move or refinance within about a decade.

Is a 10/1 ARM a good idea? It depends on your time horizon. Who should get a 10/1 ARM: Common candidates: buyers who expect to sell or refinance within 10 years, borrowers who expect income growth before the reset, and jumbo-loan borrowers where the ARM discount is large. It is riskier if you might still own the home after year 10 and could not absorb the worst-case payment shown above. This is general information, not financial advice. The 10/1 ARM pros and cons in brief: a lower starting rate with 10 years of certainty (pro) versus payment shock if you still hold the loan after the reset (con).

Options typically include refinancing into a new loan before the reset, selling the home, or making extra principal payments during the fixed period to shrink the balance that gets re-amortized. The worst-case payment in the results above shows the maximum stress-test scenario under your lifetime cap — use it to judge affordability honestly. Not financial advice.

Usually yes — most 10/1 ARMs have no prepayment penalty in the US, but check your note. Many borrowers plan to refinance near the end of the fixed period. Keep an eye on market rates in years 8–10 so you are not forced to refinance at an unfavorable time.

No — results are principal and interest (P&I) only, which is what the rate reset affects. Your total monthly housing payment will be higher once property taxes, homeowner's insurance, and any PMI or HOA dues are added. See our full mortgage payment calculator with taxes and insurance for the complete picture.

The math is exact closed-form amortization: fixed-period payment, remaining balance, and re-amortized reset payment are computed to the cent from the standard formulas. The uncertainty is in the inputs, not the math — your actual reset rate depends on the future index value, and this model assumes the reset rate holds steady after year 10 rather than adjusting annually. Treat results as estimates, not financial advice.

The classic pairing is a 30-year loan: 10 years fixed + 20 years adjustable. This calculator also supports 25, 20, and 15-year total terms (e.g., a 15-year loan = 10 years fixed + 5 years adjustable). The fixed period is always the first 10 years, since that is what "10/1" means.