Free toolsLoan amortisation
Loan amortisation schedule, month by month
Every payment split into interest and principal, with interest-only periods and a balloon handled properly. The same schedule the product puts in front of an underwriter.
Monthly payment
$3,515
Of the first amortising payment, 31.8% goes to principal.
Total interest over the term
$171.8K
$421.8K paid in total on $250K borrowed.
- Payments
- 120
- Interest as a share of what you repay
- 40.7%
Where each payment goes
- Balance outstanding
- Interest in the month
The schedule
First and last twelve months. The product exports the whole schedule to Excel as live formulas.
| Month | Payment | Interest | Principal | Balance |
|---|---|---|---|---|
| 1 | $3,515 | $2,396 | $1,119 | $248,881 |
| 2 | $3,515 | $2,385 | $1,130 | $247,751 |
| 3 | $3,515 | $2,374 | $1,141 | $246,611 |
| 4 | $3,515 | $2,363 | $1,152 | $245,459 |
| 5 | $3,515 | $2,352 | $1,163 | $244,296 |
| 6 | $3,515 | $2,341 | $1,174 | $243,123 |
| 7 | $3,515 | $2,330 | $1,185 | $241,938 |
| 8 | $3,515 | $2,319 | $1,196 | $240,741 |
| 9 | $3,515 | $2,307 | $1,208 | $239,534 |
| 10 | $3,515 | $2,296 | $1,219 | $238,314 |
| 11 | $3,515 | $2,284 | $1,231 | $237,083 |
| 12 | $3,515 | $2,272 | $1,243 | $235,840 |
| … | ||||
| 109 | $3,515 | $380 | $3,135 | $36,530 |
| 110 | $3,515 | $350 | $3,165 | $33,365 |
| 111 | $3,515 | $320 | $3,195 | $30,170 |
| 112 | $3,515 | $289 | $3,226 | $26,944 |
| 113 | $3,515 | $258 | $3,257 | $23,688 |
| 114 | $3,515 | $227 | $3,288 | $20,400 |
| 115 | $3,515 | $196 | $3,319 | $17,080 |
| 116 | $3,515 | $164 | $3,351 | $13,729 |
| 117 | $3,515 | $132 | $3,383 | $10,346 |
| 118 | $3,515 | $99 | $3,416 | $6,930 |
| 119 | $3,515 | $66 | $3,448 | $3,482 |
| 120 | $3,515 | $33 | $3,482 | $0 |
How this is computed
Anyone sizing a term loan — and anyone who has been quoted a monthly payment and wants to know what share of it is actually buying down the debt.
- The level payment is the spreadsheet PMT: principal × r ÷ (1 − (1 + r)⁻ⁿ), with r the monthly rate.
- A balloon is sized against the amortising portion only, so the monthly payment genuinely falls — which is the reason borrowers use one, and getting it wrong overstates coverage.
- Interest-only months accrue interest without touching principal, then the amortising payment is recomputed over the months that remain.
- The ledger runs at full precision; rounding happens only where the schedule is displayed. Rounding inside it once made principal repayments differ from the amount drawn.
What it will not tell you
A calculator that lists only what it does is a toy. These are the limits worth knowing before you quote the answer to anyone.
- Fees, points and prepayment penalties are not included. Ask the lender for the APR, not just the rate.
- A variable rate is modelled as if it never moves. It will.
This number belongs in a document that agrees with it.
The full plan links every one of these together and blocks export until the prose and the model reconcile. Free to generate and read.