Step 1: list the debts
One row per debt with four numbers: name, current balance, annual interest rate and minimum monthly payment. Take them from your latest statement, not from memory. Add the minimums: that sum is the least you must pay every month. Anything you can add on top of it is the extra payment.
Step 2: lay out one row per month
For each debt, build a schedule with one row per month and these columns:
| Column | What it holds | Formula |
|---|---|---|
| Month | 1, 2, 3 and so on | previous month plus 1 |
| Opening balance | What you owe at the start of the month | previous closing balance |
| Interest | Interest added this month | opening balance times annual rate divided by 12 |
| Payment | Minimum plus any extra, never more than balance plus interest | smaller of (minimum + extra) and (opening balance + interest) |
| Closing balance | What is left | opening balance + interest - payment |
The payoff month is the first month whose closing balance is zero. Total interest is the sum of the interest column. Do this for each debt and you have a plan.
Step 3: choose where the extra payment goes
Two common orderings are the debt snowball method (smallest balance first) and the debt avalanche method (highest rate first). In both, you pay the minimum on every debt and send the extra to the target debt; when a debt reaches zero, its whole payment moves to the next one. The free in-browser debt snowball calculator does this ordering; the paid workbook does not. Background: debt snowball method on Wikipedia. This page does not advise either method.
Exact worked table (free calculator figures)
Inputs, stated in full: three debts (Debt A $5,000 at 5.5% with a $150 minimum; Debt B $12,000 at 6.8% with a $250 minimum; Debt C $2,500 at 19.9% with a $100 minimum) and an extra payment of $100.00 a month. Each month the interest is balance times annual rate divided by 12, and payments are made at month end. The figures below are results of the free in-browser calculator; example figures for the example debts shown, your results depend on your own numbers; they are not results of the spreadsheet. The calculation stops at 600 months. In the snowball and avalanche rows the extra goes to the target debt and, when a debt is paid off, its whole payment moves to the next debt. The rates are illustrative, not official and not current.
| Method | Months to debt-free | Total interest | Total paid | Debt A paid off in month | Debt B paid off in month | Debt C paid off in month |
|---|---|---|---|---|---|---|
| Minimums only | 57 | $3,239.13 | $22,739.13 | 37 | 57 | 33 |
| Snowball (smallest balance first) | 37 | $2,273.75 | $21,773.75 | 24 | 37 | 15 |
| Avalanche (highest rate first) | 37 | $2,249.69 | $21,749.69 | 37 | 37 | 15 |
Reading the table: with the extra $100 a month the last debt is paid off in month 37 instead of month 57, which is 20 months earlier. Total interest falls from $3,239.13 to $2,273.75 under the snowball ordering (a difference of $965.38) and to $2,249.69 under the avalanche ordering (a difference of $989.44). The avalanche ordering costs $24.06 less interest than the snowball ordering on these debts.
The snowball ordering written out as a month-by-month plan (the total paid every month is $600 until the end):
| Months | Debt receiving the extra | Payment on that debt | Event |
|---|---|---|---|
| 1 to 15 | Debt C | $200 | Debt C reaches zero in month 15. Debts A and B get their minimums ($150 and $250). |
| 16 to 24 | Debt A | $350 | Debt A reaches zero in month 24. |
| 25 to 37 | Debt B | $600 | Debt B reaches zero in month 37. |
The payoff months in this plan are the calculator's values. In the last month of each debt the payment is smaller than the full amount shown, because only the remaining balance is paid.
Step 4: turn the plan into a tracker
A tracker is the plan plus one more column. Next to each planned closing balance, add the actual balance from your statement at month end, and a difference column (actual minus planned). A positive difference means you owe more than planned; a negative one means you are ahead. Recompute the plan from the current balances whenever a rate, a minimum payment or your extra amount changes.
What the paid workbook adds
- The schedule formulas above, already written for you, for up to 6 debts on the Debts tab.
- A Payoff Plan tab with a 120-month schedule per debt, with and without an extra payment, the payoff month, total interest, interest saved and months saved.
- A Monthly Budget tab (planned, actual, difference) that shows how much is left over to send to debt, and a Term Plan tab that spreads a lump sum over up to 26 weeks.
- US, UK and Canada versions, and a PDF guide that explains each tab with a worked example.
Limits, stated plainly: the Payoff Plan tab applies the extra payment to one chosen debt only and stops when that debt is paid off; nothing is carried over to the other debts, and the tab does not sort debts for you. Snowball and avalanche ordering belongs only to the free calculator: the rows above come from it, not from a tab of the workbook, so they will not match the tab's with-extra output. The Loan rules block on the Debts tab is left blank on purpose so you fill it from the official source. How it was checked: a script verified the structure and cell references of the workbooks and compared the example schedules to a closed-form calculation. No claim is made that the files were opened in any particular spreadsheet program.
Price, refund and licence
USD 12, one-time payment, sold on Gumroad: 3 workbooks (US, UK, CA) and a PDF guide. Licence: personal use. Refund on request within 14 days. These are the same terms as on the Gumroad listing.
Get the debt payoff planner workbooks, USD 12 on Gumroad
Other pages
Try the free debt snowball calculator. See the debt snowball spreadsheet page, the student loan payoff spreadsheet page, the budget planner template and the United States edition.