Weighted Interest Rate Calculator

A single 5% debt and a single 15% debt don't average to 10% — the larger balance determines more of the outcome. If you owe $20,000 at 5% and $5,000 at 15%, your weighted rate is 7% because the bigger debt carries more influence in the calculation.

The formula multiplies each balance by its rate, sums those products, then divides by total debt. This reveals the effective rate you're paying across your entire debt portfolio. A $30,000 mortgage at 3.5% combined with $5,000 credit card debt at 24% produces a 6.4% weighted rate — higher than the mortgage alone, but much lower than paying credit card rates on everything.

Weighted rates matter most when comparing consolidation offers. Any loan rate below your weighted average saves money immediately. Any rate above it costs more, regardless of payment simplicity. The weighted rate is your breakeven point for debt consolidation decisions.

Use this calculation when evaluating debt consolidation offers or refinancing multiple debts into a single loan. The weighted rate tells you the minimum rate needed for consolidation to save money — any offer above your weighted average costs more than keeping separate debts.

Also use it for portfolio analysis when prioritizing debt payments. The weighted rate shows your current blended cost, helping you identify which individual rates drag the average up most. Pay down debts with rates significantly above the weighted average first.

Do not use weighted rates for investment comparisons or when debts have different tax treatments. Investment returns and tax-deductible debt require separate analysis. The calculation also breaks down for debts with different payment structures — a 0% promotional rate that jumps to 24% needs special handling beyond simple weighting.

Users often calculate a simple arithmetic average instead of weighting by balance. Taking (6% + 12% + 18%) ÷ 3 = 12% ignores that a $50,000 debt at 6% has far more impact than a $2,000 debt at 18%. The unweighted average overstates the true cost by treating all debts equally regardless of size.

Another common error is including only the principal balance while excluding accrued interest or fees. Use the current total amount owed, not the original loan amount. A $10,000 credit card that now owes $10,847 should use the higher figure — otherwise the calculation understates the weighted rate.

Users also mix different rate types without conversion. Comparing a 3.5% mortgage APR with a 1.2% monthly credit card rate requires converting the credit card to annual terms (14.4% APR) first. Different compounding frequencies skew the comparison when rates aren't normalized.

The weighted average formula is: Weighted Rate = (Balance₁ × Rate₁ + Balance₂ × Rate₂ + ... + Balanceₙ × Rateₙ) ÷ Total Balance. Each debt contributes to the average proportionally based on its size relative to total debt.

Worked example: $15,000 at 6% plus $10,000 at 12% equals ($15,000 × 0.06 + $10,000 × 0.12) ÷ $25,000 = ($900 + $1,200) ÷ $25,000 = 8.4%. The larger 6% debt pulls the average below the simple arithmetic mean of 9%.

The calculation assumes annual percentage rates and equal compounding periods. If debts compound at different frequencies (monthly vs daily), convert all rates to annual effective rates first. For variable-rate debts, use current rates — the weighted average changes as individual rates adjust.

Lenders use weighted average cost of capital (WACC) as the hurdle rate for approving consolidation loans. Your weighted debt rate above 12-15% signals high credit risk, often disqualifying you for the low rates needed to make consolidation worthwhile — a catch-22 where those who need consolidation most can't access it.