How to Calculate Which Debt to Pay Off First on $64,500 Across 5 Debt Types: The Formula for the Fed's September 2026 Rate Decision
The Wednesday Problem
As of Monday, September 14, 2026, mortgage rates are back over 7%, and NerdWallet's daily rate coverage points to the reason: markets now expect the Fed to raise the federal funds rate at Wednesday's meeting. That expectation is already priced into mortgage rates — and it's about to reprice something else in your financial life if you're carrying a HELOC or are considering opening one: your variable-rate debt.
If you're sitting on a mix of credit cards, a personal loan, an auto loan, student loans, and medical debt, this week is a genuinely bad time to guess at your payoff order. The math changes depending on whether a HELOC's rate is about to move, whether a balance transfer offer is worth the fee, and how much of your "extra payment" budget survives August's inflation numbers (CPI +0.4% for the month, per the Bureau of Labor Statistics). Below is the formula, worked on a five-debt, $64,500 example — but the point isn't the example. It's that you need to run this with your own balances, your own rates, and your own budget.
The 5-Variable Formula
Every debt in your stack can be scored on the same five inputs:
- Balance — what you owe right now
- APR — the interest rate, and whether it's fixed or variable
- Minimum payment — your contractual floor
- Months remaining on any promotional or intro rate — this is the variable people forget, and it's the one that makes balance transfers either brilliant or a trap
- Behavioral risk — how likely you are to re-run a balance up after you pay it down, or to derail the plan entirely
The first three variables let you calculate a number most people never compute: monthly interest cost, not just APR. That's balance × (APR ÷ 12). It reranks your debts by actual dollars bleeding out every month, which sometimes disagrees with a simple "highest rate first" ranking once you add HELOC or balance transfer options into the mix.
The Example: $64,500 Across 5 Debt Types
Here's an illustrative stack — your numbers will differ based on your specific situation, but the structure is common:
| Debt | Balance | APR | Min. payment | Monthly interest cost |
|---|---|---|---|---|
| Credit card A | $9,800 | 24.99% | $245 | $204.08 |
| Credit card B | $6,200 | 22.99% | $155 | $118.78 |
| Personal loan | $12,500 | 13.5% | $410 | $140.63 |
| Auto loan | $18,000 | 7.2% | $525 | $108.00 |
| Student loan | $11,000 | 5.8% | $180 | $53.17 |
| Medical debt | $7,000 | 0% (provider plan) | $200 | $0 |
| Total | $64,500 | — | $1,715 | $624.66 |
That $624.66 is what this person is paying every single month just to keep the balances flat, before a single dollar goes toward principal beyond the minimums. Say they've found $700/month in extra budget to throw at debt. Where should it go?
This is the kind of analysis Kovarino runs for you — so you don't have to build the spreadsheet yourself — but let's walk through it by hand once so you know what's happening underneath.
Strategy 1: Straight Avalanche
Avalanche order ranks by APR: Card A (24.99%) → Card B (22.99%) → Personal loan (13.5%) → Auto (7.2%) → Student loan (5.8%) → Medical (0%).
Put the $700 extra on Card A. Payment becomes $945/month. Using the standard amortization formula (months = -ln(1 - r×B÷P) ÷ ln(1+r), where r is the monthly rate), Card A clears in about 12 months, at a cost of roughly $1,540 in interest.
Roll that $945 plus Card B's $155 minimum into Card B — $1,100/month. Card B clears in about 6 months, costing roughly $400 in interest.
Total: 18 months, $1,940 in interest, to clear both cards.
Strategy 2: Balance Transfer
Now assume a 0% intro APR balance transfer offer for 18 months, 3% transfer fee, on both cards combined ($16,000). Transfer fee: $480 upfront.
Apply the same combined $1,100/month (minimums + extra) to the $16,000 balance at 0% interest: $16,000 ÷ $1,100 ≈ 14.5 months to payoff — inside the 18-month window.
Total cost: $480 (fee only). Interest paid: $0.
That's $1,460 cheaper than avalanche on this specific pair of cards, and it finishes 3.5 months faster. The catch — and it's a real one — is variable 5, behavioral risk: this only works if the cards get paid off and stay paid off before the promotional rate expires and reverts to a standard purchase APR, often north of 24%. If the two paid-off cards get used again (a real risk NerdWallet's coverage of sports betting debt highlights: people tend to reward themselves for progress by spending against newly-freed credit), the math flips fast.
Strategy 3: HELOC Consolidation
With mortgage rates over 7% as of this week, a HELOC in the 8.25% range is plausible for a borrower with sufficient equity. Say this person can draw $28,500 to pay off both cards and the personal loan in one move, applying $1,510/month (all three minimums plus the $700 extra) toward the HELOC balance.
r = 0.0825 ÷ 12 = 0.006875. Running the same amortization formula: payoff in about 20.3 months, total interest around $2,138.
That's more total interest than avalanche paid on the cards alone ($1,940) — but it's also consolidating three debts, not two, and it drops the effective rate on the personal loan piece from 13.5% to 8.25%. The real wildcard is variable 2: HELOC rates are variable and tied to the prime rate, which moves with the Fed. If Wednesday's decision goes the way markets expect, this 8.25% estimate could be stale within days — and a rate that drifts upward over a 20-month payoff window changes this calculation materially. If you're weighing a HELOC against consolidation right now, Avalanche vs. Balance Transfer vs. HELOC on $69,500 in Mixed Debt walks through the same rate-sensitivity question in more depth.
Side-by-Side
| Strategy | Debts covered | Time to payoff | Total cost | Primary risk |
|---|---|---|---|---|
| Avalanche | 2 credit cards | 18 months | $1,940 interest | None — fixed, known |
| Balance transfer | 2 credit cards | 14.5 months | $480 fee | Re-spending after payoff; rate reversion if not paid in time |
| HELOC | 2 cards + personal loan | 20.3 months | $2,138 interest (est.) | Variable rate could rise post-Fed |
Notice that the HELOC "loses" on pure interest cost in this example even though it's consolidating more debt — because it's absorbing the auto and student loan APRs' better company, not beating them. That's a detail a lot of "just get a HELOC and consolidate everything" advice glosses over. The auto loan (7.2%) and student loan (5.8%) in this example are already cheaper than an 8.25% HELOC — moving them into the HELOC would make things worse, not better. Consolidation only helps the debts it's actually cheaper than.
The Variable Nobody Puts in the Spreadsheet
August's jobs numbers — payroll employment up 162,000, unemployment holding at 4.1%, per the BLS — plus CPI running +0.4% for the month, are the reason the $700/month "extra payment" assumption above is fragile. If grocery and everyday costs keep climbing at that pace, the actual dollar amount available for accelerated payoff shrinks month to month, which changes every timeline calculated above. This is also why "die with zero" thinking — spending down assets deliberately rather than hoarding — only makes sense after the debt foundation is handled. NerdWallet's coverage of that philosophy is explicit that it requires financial stability first; running a payoff plan on money that may not be there next quarter is the opposite of that foundation.
The behavioral piece matters just as much as the math. A debt snowball approach — smallest balance first, regardless of rate — costs more in raw interest than avalanche in almost every case, but it's built around the same psychology NerdWallet flags in its sports betting debt coverage: quick wins keep people in the plan. If you know you're the type who needs the medical debt ($7,000, 0% APR) crossed off the list for momentum even though it's mathematically the last thing you should prioritize, that's a legitimate variable five input — not a failure of discipline. The $6,900 gap between avalanche and consolidation on a similar-sized debt stack shows how much that behavioral choice can cost, and whether it's worth it.
One more temptation worth naming: opening a new rewards card mid-payoff. NerdWallet's own coverage calls the Chase Sapphire cards a "must-have for travelers" for good reason — but a new card with a big welcome bonus, opened while you're two cards deep into a payoff plan, is exactly the kind of decision that resets your behavioral risk score to high. It's not that rewards cards are bad; it's that timing them during an active debt payoff undermines the plan you just built.
Run Your Own Numbers
The $64,500 example above used a specific mix of rates, balances, and a specific $700 extra-payment budget. Change any one of those five variables — a higher APR on your largest card, a shorter intro period on your balance transfer offer, a HELOC rate that moves after Wednesday, or less extra cash than you assumed — and the winning strategy can flip entirely. If your stack also includes a chunk of federal student loans alongside credit cards, the 43K student loan plus mixed debt breakdown is a closer analog than this one.
You can model this for your specific situation at Kovarino — enter your actual balances, rates, and available offers, and get the payoff sequence and consolidation comparison run against your numbers, not a hypothetical stack. With a Fed decision landing Wednesday and rates already moving, this is one of those weeks where "close enough" math can cost real money.
Sources
- Mortgage Rates Today, Monday, September 14: Over 7% — NerdWallet
- Mobile Sports Betting Is Booming — So Is the Debt That Comes With It — NerdWallet
- Should You Really Try to ‘Die with Zero’? — NerdWallet
- Major Economic Indicators Latest Numbers — Bureau of Labor Statistics
- 7 Reasons NerdWallet Calls Chase Sapphire a “Must-Have for Travelers” — NerdWallet