10/1 ARM Mortgage Calculator
The 10/1 ARM mortgage calculator estimates payments for an adjustable-rate mortgage that stays fixed for ten years and then resets annually. Enter the loan balance, term, opening rate, expected yearly adjustment, and lifetime cap to see the first payment, the possible later payment range, paid interest, and total payments.
How to use
- Enter the mortgage balance or loan amount you want to model.
- Set the term in years. A 20- or 30-year term is common, but the calculator accepts shorter comparisons.
- Add the initial interest rate that applies during the first 10 years.
- Enter an expected yearly adjustment after the fixed period and the highest rate allowed by the loan’s cap.
- Add optional closing or finance costs if you want the total payment figure to include them.
The result is a projected range, not a promise from a lender. Real ARM contracts can include initial adjustment caps, periodic caps, margins, and indexes, so use the loan estimate for final planning.
How it works
During the fixed period, the calculator uses the standard amortizing mortgage payment formula. Beginning in month 121, it recalculates the payment once each year using the remaining balance, remaining months, and the adjusted rate. The adjustment is limited by the lifetime cap you enter. Interest is then accumulated month by month so the total reflects the changing schedule.
This makes the calculator useful for stress-testing an ARM against a mortgage calculator, estimating refinancing risk with a loan calculator, or checking how the payment fits into a budget calculator.
Formula
For each rate period, the monthly principal-and-interest payment is:
where $B$ is the current balance, $r$ is the monthly interest rate, and $n$ is the remaining number of monthly payments. If the rate is 0%, the payment is simply the balance divided by remaining months.
Example
| Scenario | Value |
|---|---|
| Balance | $250,000 |
| Term | 20 years |
| Initial rate | 5.75% |
| Annual adjustment | 0.25 percentage points |
| Lifetime cap | 8.25% |
With these assumptions, the payment starts near $1,756 per month and may rise as the rate resets after year 10.
Common mistakes
- Comparing only the first payment instead of the payment after the reset period.
- Ignoring the lifetime cap and adjustment rules in the lender’s disclosure.
- Treating an ARM projection as guaranteed; the actual index path can be higher or lower.