Enter your mortgage details
Example data table
| Item | 15-Year | 30-Year |
|---|---|---|
| Loan amount | $350,000 | $350,000 |
| Rate | 6.250% | 6.750% |
| Points | 0.500% | 0.000% |
| Closing costs | $2,500 | $2,500 |
| Annual tax | $4,200 | $4,200 |
| Annual insurance | $1,500 | $1,500 |
| Result: Monthly P&I | Varies | Varies |
| Result: Total interest | Varies | Varies |
| Result: Payoff time | 15 years | 30 years |
Formula used
Monthly principal and interest payment (standard amortizing loan):
Extra payments are applied to principal, reducing the balance faster and lowering total interest. Upfront costs are computed as points (percent of loan) plus closing costs.
How to use this calculator
- Enter the loan amount you plan to borrow.
- Provide rates for both 15-year and 30-year options.
- Add points and closing cost estimates for each option.
- Include taxes, insurance, and any monthly add-ons.
- Add extra payments to see payoff and interest changes.
- Click calculate to view results and download files.
Professional notes
Payment difference and cash flow pressure
On a $350,000 loan, a 15-year term usually produces a higher monthly principal-and-interest payment because the balance is repaid in 180 months instead of 360. Even a small rate gap can magnify the difference. Use the calculator to compare monthly totals after adding taxes, insurance, HOA, PMI, and any extra principal.
Interest cost over the full repayment horizon
Total interest is driven by three factors: rate, balance, and time. The 30-year term keeps a larger balance outstanding for longer, so it often accumulates substantially more interest, even when the monthly payment feels comfortable. The results section shows interest totals side by side and highlights estimated interest saved. If rates are equal, the term length alone can still create a large lifetime interest spread.
Upfront costs, points, and practical break-even
Discount points and closing fees affect your first-day outlay. Points are calculated as a percent of the loan amount, then combined with closing costs to form an upfront cost figure for each option. The calculator estimates an all-in break-even month by tracking cumulative outlay over time, including upfront costs and monthly totals. A later break-even may matter if you expect to refinance or move sooner.
Extra payments and accelerated payoff outcomes
Adding extra principal reduces the outstanding balance faster, which lowers future interest charges and shortens payoff time. You can model different strategies, such as paying the 30-year loan like a 15-year by setting the 30-year extra payment near the 15-year payment difference. The payoff-time metric updates instantly. Compare how quickly each option reaches milestones like 80% loan-to-value.
Decision signals to review before choosing
Use the comparison when making trade-offs: higher payment versus lower interest, faster equity build versus liquidity flexibility, and upfront costs versus long-run savings. If job stability or emergency reserves matter most, the 30-year option with voluntary extra payments can provide control. If predictability and minimum interest are priorities, the 15-year option may align better. Confirm the choice with your holding period.
FAQs
1. What does monthly total include here?
Monthly total adds principal and interest, any extra payment, estimated monthly tax and insurance, plus HOA and PMI. Utilities and maintenance are excluded, and taxes or insurance can change over time.
2. How are points handled?
Points are treated as an upfront cost equal to a percent of the loan amount. They do not change the rate automatically in this tool; enter the rate you expect after points are applied.
3. Why can a 30-year still be cheaper overall?
If the 30-year rate is much lower, or if you invest the payment difference at a higher return, the long-term outcome can shift. This calculator focuses on loan cash flows, not investment returns.
4. What is the break-even month?
It is the first month where the 15-year cumulative outlay becomes less than or equal to the 30-year cumulative outlay, including upfront costs and monthly totals. It is an estimate for comparison.
5. How do extra payments affect the schedule?
Extra payments are applied to principal each month, lowering the balance faster. That reduces interest and shortens the payoff time, which you will see in both the payoff metric and total interest.
6. Is the amortization exact to the penny?
The schedule uses standard monthly compounding with rounding displayed to two decimals. Real servicers may apply slightly different rounding rules, escrow adjustments, or timing conventions.