Debt Payoff Calculator (Free Spreadsheet)

Debt feels endless precisely because nobody ever shows you the end. A balance and a minimum payment tell you what you owe today; they carefully avoid mentioning the two numbers that actually matter — when you’ll be done, and what the ride will cost.

This calculator computes both for every debt you have, using real amortization math (the NPER formula — the same calculation lenders use), not a rough division. Enter three numbers per debt: balance, APR, monthly payment. We verified every output against an independent calculation before publishing; the worked example ships in the file.

What the example reveals

Four typical debts — two credit cards, a car loan, a student loan — totaling $27,550 with $670/month going at them:

The $2,400 credit card at 22.99% takes 26 months and costs $655 in interest at $120/month. The small $850 card is gone in 17 months. The car loan clears in 36 months. And the student loan — biggest balance, lowest rate — grinds along for 101 months with $3,638 of interest, more than half the example’s $5,483 total interest bill.

Two lessons hiding in those numbers:

Why division lies to you. $2,400 ÷ $120 suggests 20 months; the real answer is 26. The extra six months are interest quietly eating half of each early payment. That gap grows brutally as rates rise — which is why this sheet uses amortization math and also flags the nightmare case: if a payment doesn’t even cover the monthly interest, the cell says “payment too low” instead of pretending a payoff date exists.

Order matters less than people argue about. Snowball (smallest balance first — sort the rows by balance) buys motivation: the example’s $850 card dies fast and frees up $60/month. Avalanche (highest APR first — sort by APR) saves the most interest. The honest math: for most real debt sets the dollar difference is modest, and the method you’ll stick with wins. The calculator shows you both orderings in two clicks of sorting.

Using it as a payoff plan, not just a snapshot

The sheet models fixed payments — here’s how to use that to plan:

Find your snowball payment. When a debt hits zero, its payment doesn’t return to your lifestyle; it moves to the next debt’s row. Re-enter the new payment and watch that debt’s months collapse. In the example, rolling the dead $850 card’s $60 into card A cuts card A’s remaining timeline by months.

Test “what if I add $50?” Change one payment cell and the months and interest update instantly. Seeing “+$50/month = 7 months sooner and $180 less interest” is the most motivating arithmetic in personal finance, and it’s exactly what the worksheet is for.

Freeze the inputs monthly. Balances drop as you pay; update them at each month’s start. Watching the total row shrink is the progress bar.

New charges on a card break the model, of course — the calculator assumes the balance only goes down. That assumption is also the plan.

Using it in Google Sheets

1. Google Sheets → blank sheet → File → Import → Upload → select the file → Replace spreadsheet. NPER works identically there.
2. Sort rows by balance (snowball) or APR (avalanche) — the formulas travel with the rows.

Free up the extra payment with the subscription tracker, and once a debt dies, redirect its payment into a savings goal — the same habit, pointed forward. (This is general information, not financial advice; for complex situations — consolidation, hardship programs — a nonprofit credit counselor is worth a call.)

Frequently asked questions

My card’s APR changed — now what? Update the cell. Variable rates mean the projection is a current-conditions estimate, which is still infinitely better than no end date.

Where do minimum payments fit in budgets? Minimums are a “need”; anything extra is savings-like. Our 50/30/20 calculator is set up exactly that way.

Is it free? Free for personal and commercial use, no signup. Numbers look off? Tell us — we re-verify against independent math and fix the file.