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Debt Calculator

Managing multiple debts requires understanding your true repayment costs and available strategies. This calculator compares four distinct approaches—minimum payments, debt snowball, debt avalanche, and consolidation—to show which minimizes interest, accelerates payoff, or best suits your budget. Input up to six debts with their balances, rates, and current payments to instantly see payoff timelines and total interest charges across all strategies.

Last updated:

Creators Małgorzata Koperska, MD
6,823 people find this calculator helpful

What Is Debt?

Debt arises when one party borrows money from another with an agreement to repay it, typically with added interest. The most widespread sources are institutional loans: mortgages, auto loans, student loans, personal loans, and credit cards. When you accept a loan, you commit to returning the principal plus accrued interest by a specified date. The loan's term, interest rate, and compounding frequency determine how much you ultimately owe.

Understanding debt structure is essential because different loans behave differently. A credit card charging 18% APR compounds monthly, while a mortgage at 4% compounds across a 30-year amortization. The total cost depends not only on the rate but also on how quickly you pay down the balance.

Debt Repayment Strategies

Four primary approaches exist for managing multiple debts:

  • Minimum payments: Pay only the required monthly amount on each debt. This method maximises total interest paid and extends your payoff timeline, but requires minimal monthly discipline.
  • Debt snowball: Pay minimums on all debts, then direct extra funds to the smallest balance first. Once the smallest debt vanishes, roll that payment into the next target. Psychologically rewarding but mathematically inefficient.
  • Debt avalanche: Pay minimums on all debts, then attack the highest interest rate first. This method minimises total interest and accelerates payoff, but requires patience on high-balance accounts.
  • Consolidation: Combine multiple debts into a single loan at one rate. Simplifies bookkeeping and can reduce interest if the new rate is lower, though origination fees may offset savings.

How the Calculator Works

The calculator aggregates your debt portfolio and applies each strategy to estimate total interest, effective APR, and months to payoff. It compounds interest monthly on each debt, applies your payments according to the chosen strategy, and simulates month-by-month until all balances reach zero. For consolidation, it factors in any upfront fees and recalculates based on the new loan's term and rate.

Total Debt = Sum of all debt balances (Debt₁ + Debt₂ + ... + Debt₆)

Total Monthly Payment = Sum of all minimum payments (Pmt₁ + Pmt₂ + ... + Pmt₆)

Effective Debt APR = Weighted average APR based on balances and rates

Interest Charged = Total amount paid − Total Debt

Payoff Time = Number of months until all balances = £0

  • Debt balance — Outstanding balance on each loan or credit account
  • Interest rate (APR) — Annual Percentage Rate charged on the debt
  • Minimum payment — Required monthly payment amount
  • Consolidation rate — APR of the new consolidation loan
  • Prepaid fee — Upfront origination or closing cost (if applicable)

Common Pitfalls and Considerations

Avoid these mistakes when evaluating your repayment strategy.

  1. Ignoring rising interest rates — If any of your debts carry variable rates (common on credit cards), your monthly interest charge can spike unexpectedly. Always request the worst-case rate or current offer terms before committing to a payoff timeline.
  2. Underestimating consolidation fees — A consolidation loan often charges origination, appraisal, or closing fees (1–5% of the loan amount). Verify the all-in cost: sometimes the new monthly payment saves money, but fees make the total cost higher. Run both scenarios.
  3. Overstating extra payment capacity — Your calculator input should reflect realistic monthly capacity. Life happens—medical bills, job loss, home repairs. A strategy requiring large extra payments may fail within months. Choose a sustainable tier.
  4. Forgetting the new debt risk — Consolidation creates one large debt. If you continue old spending habits, you'll owe both the consolidated loan and new charges. Budget discipline matters more than the strategy itself.

Using This Calculator

Enter the number of debts (2–6) and provide each debt's balance, annual interest rate, and your current minimum monthly payment. If considering consolidation, also enter the loan's interest rate and any upfront fees. The calculator will instantly show payoff timelines and total interest for all four strategies, allowing direct comparison.

The simulation assumes you maintain your stated payments or higher. If you plan to reduce payments, the timeline will extend and interest will increase. Monthly minimum payments are modelled as gradually decreasing once balances drop, simulating typical amortization. Fixed-rate debt products (mortgages, car loans) and variable-rate products (credit cards) are both supported.

Frequently Asked Questions

What is the difference between the debt snowball and debt avalanche methods?

The snowball targets the smallest balance first regardless of interest rate, creating quick psychological wins as debts disappear. The avalanche targets the highest interest rate first, mathematically minimising total interest paid. Most people save £500–£2,000 by switching from snowball to avalanche, depending on the number and mix of debts. Avalanche requires more discipline because high-balance, high-interest debts (often credit cards) take longer to eliminate.

Should I consolidate my debts into a single loan?

Consolidation makes sense if the new loan's rate is notably lower than your weighted average rate, and the combined fees don't erase savings. Use a consolidation calculator to compare: take your total interest under the avalanche method and subtract the new loan's interest and all upfront fees. If the difference is positive, consolidation saves money. A secondary benefit is simplified accounting—one payment instead of six—though this doesn't lower costs.

How does the calculator estimate my payoff time?

The tool simulates month-by-month repayment. Each month, it applies interest to each debt based on its APR and current balance, deducts your payment according to your chosen strategy, and repeats until all balances hit zero. The simulation captures compounding accurately and accounts for payment timing within the month. Results assume you maintain consistent payments; real payoff may differ if you skip payments or rates change.

Why does my monthly payment decrease over time with the minimum payment strategy?

Most loans—mortgages, car loans, and some credit cards—apply payments first to interest, then to principal. Early payments cover mostly interest; later payments cover mostly principal. As your balance shrinks, the interest portion of the required minimum falls, so the minimum payment itself decreases. This is built into typical loan amortization tables and is reflected in the calculator's payoff estimates.

Can I use this calculator if my debts have different payment types (fixed vs. variable)?

Yes. The calculator handles a mix of fixed-rate loans (mortgages, personal loans) and variable-rate products (credit cards). For credit cards with variable rates, enter your current APR or a conservative estimate of the rate you expect. Keep in mind that if rates rise, your actual payoff time and total interest will increase beyond the calculator's estimates.

What fees should I include for a consolidation loan?

Include all upfront costs: origination fees, appraisal fees, credit report fees, title fees (for secured loans), and any prepayment penalties on your current debts if you pay them off early. Some lenders roll fees into the loan balance, increasing the amount borrowed and total interest. Others charge upfront. Always clarify with your lender and enter the total upfront cost or the rolled-in fee amount so the calculator reflects your true borrowing cost.

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