10/1 ARM Mortgage Calculator
A 10/1 ARM locks your rate for the first 10 years, then adjusts once a year for the remaining term. Enter your loan details below to see your initial payment, the highest possible payment under your rate caps, total interest cost, and a full year-by-year amortisation schedule. A side-by-side comparison with a 30-year fixed rate is also shown so you can weigh the trade-offs at a glance.
What is a 10/1 ARM?
A 10/1 adjustable-rate mortgage charges a fixed interest rate for the first 10 years of the loan, then resets the rate once every 12 months for the remainder of the term (typically 20 more years on a 30-year loan). The "10" denotes the initial fixed period and the "1" denotes how often the rate can change after that. Because lenders take on less long-term interest rate risk with an ARM, they typically offer a lower starting rate than a comparable 30-year fixed loan, which translates into a lower initial monthly payment.
How the rate caps work
Three caps govern how much your rate can move. The first adjustment cap limits the increase at the very first reset (for example, 2% or 5% depending on your loan). The periodic cap limits each subsequent annual change (commonly 2%). The lifetime cap sets the ceiling above your starting rate over the entire life of the loan (commonly 5% or 6%). Using a 5.75% start rate with a 2/2/5 cap structure as an example: after year 10 the rate can jump at most to 7.75%, then at most 9.75% the following year (but no higher than 10.75% ever, since 5% is the lifetime ceiling above 5.75%). Enter your own caps above to see the worst-case scenario for your specific loan.
When a 10/1 ARM makes sense
A 10/1 ARM is worth considering when you expect to sell or refinance the property before the first adjustment in year 11. The lower initial rate reduces your payment and interest during the fixed window. It may also suit borrowers who expect income to grow significantly, so that a higher payment in year 11 will be affordable. Conversely, if you plan to stay in the home for 20 or 30 years and rates rise, the total interest cost of an ARM can exceed that of a fixed-rate loan. Use this calculator's comparison panel and amortisation schedule to model both scenarios with your actual numbers.
Understanding payment shock
Payment shock refers to the increase in your monthly payment when the ARM resets after the fixed period. Even a 2% rate rise on a $320,000 balance can add several hundred dollars per month. This calculator shows you the worst-case maximum payment under your lifetime cap so you can test whether that payment fits your future budget. Building an emergency fund equal to several months of the maximum payment is a prudent safeguard if you keep the loan into the adjustable phase.
Typical 10/1 ARM cap structures
| Cap structure | First adjustment | Per-year after | Lifetime | Risk level |
|---|---|---|---|---|
| 2/2/5 | 2% | 2% | 5% | Moderate |
| 2/2/6 | 2% | 2% | 6% | Moderate-High |
| 5/2/5 | 5% | 2% | 5% | High at first reset |
| 5/5/5 | 5% | 5% | 5% | High |
The most common cap combinations quoted by US lenders. Your loan documents are the authoritative source.
Frequently asked questions
How is the 10/1 ARM payment calculated?
During the first 10 years, your monthly principal and interest payment is calculated like a standard fixed-rate loan: P x r(1+r)^n / ((1+r)^n - 1), where P is the loan amount, r is the monthly rate (annual rate / 12), and n is the total number of months. After year 10, the same formula is applied each year using the new (adjusted) rate and the remaining balance and remaining term.
What index do 10/1 ARMs use?
Most US 10/1 ARMs written after 2021 use SOFR (Secured Overnight Financing Rate) as their benchmark index. Older loans may reference the 1-year CMT (Constant Maturity Treasury) or the LIBOR replacement rate. Your lender adds a fixed margin (typically 2.25 to 3.5 percentage points) to the index to set your rate at each adjustment. The sum of index plus margin cannot exceed the cap limits in your loan documents.
Is a 10/1 ARM the same as a 10-year fixed mortgage?
No. A 10-year fixed mortgage is fully paid off in 10 years with higher monthly payments. A 10/1 ARM has a 30-year (or chosen) amortisation schedule but merely fixes the rate for the first 10 years. After year 10, the 10/1 ARM still has 20 years of payments remaining at a variable rate. A 10-year fixed mortgage gives you a lower total cost but demands a much higher monthly payment.
Can I refinance out of a 10/1 ARM before it adjusts?
Yes. Refinancing before the first adjustment date (month 121 on a 30-year loan) is a common strategy. Check whether your loan has a prepayment penalty and factor in closing costs (typically 2-5% of the loan balance) before deciding. If prevailing fixed rates are still reasonable near year 10, refinancing into a 20-year fixed can lock in a stable payment for the remaining term.
How does PMI apply to an ARM?
PMI rules are the same as for a fixed-rate loan. If your down payment is less than 20% of the home's value, the lender will require private mortgage insurance. PMI is usually cancelled automatically once you reach 80% LTV (the balance equals 80% of the original purchase price), or you can request cancellation at that point. Because an ARM's lower initial payment means slightly slower equity buildup in the early years, it can take a little longer to cross the 80% LTV threshold.
What is the difference between a 10/1, 7/1, and 5/1 ARM?
The number before the slash is the initial fixed-rate period in years. A 10/1 ARM fixes the rate for 10 years, a 7/1 for 7 years, and a 5/1 for 5 years. In each case, the "1" means the rate can reset annually thereafter. Shorter fixed periods usually (but not always) offer a lower starting rate as compensation for taking on rate risk sooner. A 10/1 ARM strikes a balance between a low rate and a long runway before the first adjustment.