PALLAS / CALCULATOR
Loan Calculator
Calculate a fixed-rate, fully amortising monthly loan payment, total interest and payoff time. Add an optional extra monthly payment to see how much time and interest it can remove.
INPUT
Enter values
Method & formula
The calculator uses the standard fixed-rate amortisation formula for the scheduled principal-and-interest payment, then simulates the outstanding balance month by month. Interest is calculated from the remaining principal; optional extra payments reduce principal and can shorten the payoff period.
- Monthly rate = annual nominal rate / 12
- Scheduled payment = P × r / (1 − (1 + r)^−n)
- Monthly interest = opening balance × monthly rate; principal paid = payment − interest
Example
A fixed-rate loan produces the same scheduled principal-and-interest payment each month, but early payments contain more interest because the outstanding balance is higher. Extra principal payments reduce later interest.
Sources & standards
FAQ
Does this include taxes, insurance or lender fees?
No. It models principal and interest only. Taxes, insurance, closing costs, servicing fees and jurisdiction-specific charges must be added separately.
What does the extra monthly payment do?
It is added after the scheduled payment and applied to principal in this model. The calculator then recomputes the actual payoff month and interest total.
Can real lender calculations differ?
Yes. Daily interest accrual, odd first periods, fees, rounding rules, adjustable rates and prepayment terms can change real statements. This is a deterministic fixed-rate monthly model.