Loan Inputs
Example Data Table
This example uses the prefilled default inputs shown in the form.
| Scenario | Loan | Term | Start Payment | Peak Payment | Total Interest | Total Cost (incl. upfront) |
|---|---|---|---|---|---|---|
| Example | Fixed | 30 years | $1,896.20 | $1,896.20 | $382,633.47 | $686,133.47 |
| Example | ARM | 30 years | $1,750.72 | $2,504.09 | $508,893.43 | $814,893.43 |
Numbers are projections, not offers or quotes.
Formula Used
Fixed Payment
Monthly payment uses the standard amortization formula: PMT = P × r × (1+r)n / ((1+r)n − 1), where P is principal, r is monthly rate, and n is total months.
Monthly Breakdown
Each month: Interest = Balance × r, Principal = Payment − Interest, then balance reduces by principal plus any extra payment.
ARM Rate Path
At each adjustment: TargetRate = Index + Margin. The model applies a floor, then caps: periodic cap limits per-adjustment change, and lifetime cap limits the maximum rate as InitialRate + LifetimeCap.
How to Use This Calculator
- Enter the loan amount, term, and choose a currency symbol.
- Fill the fixed-rate details, including optional extra payments and costs.
- Fill the adjustable details: intro years, index, margin, and caps.
- Set an index drift value to model rising or falling rates.
- Click Compare Loans to see totals and break-even months.
- Download CSV schedules or a PDF report for sharing.
Notes
- This is an educational projection based on your assumptions.
- Real ARM adjustments depend on lender rules and index publication timing.
- Taxes, insurance, and HOA dues are not included in payments.