Calculator
Example data table
| Year | Payments | Principal | Interest | Fees | Ending balance |
|---|---|---|---|---|---|
| 2026 | $6,240.00 | $4,380.50 | $1,650.25 | $209.25 | $20,619.50 |
| 2027 | $6,240.00 | $4,748.15 | $1,307.60 | $184.25 | $15,871.35 |
| 2028 | $6,240.00 | $5,146.20 | $1,012.40 | $81.40 | $10,725.15 |
Formula used
The periodic payment for an amortizing loan is computed using the standard present value annuity formula. For each period, interest is calculated on the current balance, and the remaining portion of the payment reduces principal.
- Extra principal accelerates payoff by reducing the balance faster.
- Interest-only periods pay interest first; amortization starts later.
- Interest tax is modeled as a percentage of the interest portion.
How to use this calculator
- Enter the loan amount, APR, and term in years.
- Select your payment frequency and start date.
- Add optional items like fees, interest tax, or interest-only periods.
- Click Calculate to view annual totals above the form.
- Download CSV for full detail, or PDF for sharing.
Annual budgeting using calendar-year totals
The annual table groups payments by calendar year from your selected start date. This is useful for budgets, taxes, and cash planning because it reflects what leaves your account within each year. Year one often looks different when the loan starts mid-year, or when payoff happens before December. Use the Year 1 payment total card as a quick baseline for near-term planning. It also aligns loan planning with annual income and expense cycles.
Interest patterns and cost drivers
Interest is calculated each period on the remaining balance, so interest generally declines as principal is repaid. Higher APR and longer terms increase total interest because the balance stays larger for longer. If you apply an interest tax rate, the model adds a surcharge to the interest portion only, which increases annual cash outflow without changing the principal payoff mechanics.
Fees, one-time charges, and capitalization
The calculator separates per-period fees from one-time fees so you can test true servicing costs versus upfront charges. When “Add one-time fee to loan balance” is enabled, that fee becomes part of the financed amount and can increase interest expense. When it is disabled, the fee is treated as an upfront cash payment, which affects total paid but does not accrue interest.
Extra principal and payoff acceleration
Adding extra principal per period reduces the balance faster, which shortens the payoff date and typically lowers total interest. A small recurring extra payment can outperform a single late lump sum because it eliminates interest earlier in the schedule. Run two scenarios—zero extra and your target extra—to compare the payoff date, annual totals, and cumulative interest.
Reporting workflow for reviews and approvals
Use the Plotly graph to see how principal, interest, and fees shift by year and to track the ending balance. Export CSV for audit-ready detail, including period dates and balances, or export PDF for a compact summary suitable for sharing. For consistent comparisons, keep the same start date and frequency while changing only one assumption at a time.
FAQs
What does “per period” mean in the result?
It is the scheduled payment for your chosen frequency, such as monthly or quarterly. Annual totals are shown separately in the annual breakdown table.
Why can Year 1 payments look higher or lower?
Year 1 is grouped by calendar year from your start date. A mid-year start or early payoff can create partial-year totals that differ from later years.
How is interest tax calculated here?
Each period’s interest is multiplied by the interest tax rate. That amount is added to cash outflow but does not reduce principal or change the interest calculation base.
What happens during interest-only periods?
The payment covers interest plus optional extra principal, fees, and tax. After the interest-only phase, the payment is recalculated to amortize the remaining balance.
Does capitalizing the one-time fee increase total interest?
Often yes. When the fee is added to the loan balance, it can accrue interest over time. Paying it upfront avoids interest on that fee amount.
Can I model weekly or biweekly payments?
This version supports monthly, quarterly, semiannual, and annual schedules. For other frequencies, use the closest option and validate with lender disclosures for exact timing.