Debt calculator
Weighted Average Interest Rate Calculator
Estimate the blended interest rate across several balances by weighting each rate by the amount owed. This is useful when a single simple average would hide which loan or card balance drives the most interest cost.
Calculate weighted average rate
Formula
Weighted average interest rate equals the sum of each balance multiplied by its annual rate, divided by the sum of all balances. In shorthand: (balance × rate + balance × rate + balance × rate) ÷ total balance.
Worked example
If one balance is $1,000 at 10% and another is $3,000 at 20%, the simple average rate is 15%, but the weighted average is 17.50%. The larger 20% balance carries more weight, so the blended rate is closer to 20% than 10%.
How to interpret the result
The weighted rate is a summary of the listed balances, not a payoff plan. It can help explain the overall interest burden across cards, personal loans, auto loans, student loans, or other fixed balances. It does not show monthly payments, amortization, compounding details, fees, variable-rate changes, or creditor-specific payment allocation rules.
For payoff timing, use this page alongside the debt payoff calculator or debt avalanche calculator. To compare two new borrowing offers instead of existing balances, use the loan comparison calculator.
Common mistakes
- Using a simple average when balances are very different.
- Mixing promotional APRs, purchase APRs, and cash-advance APRs without noting which balance each rate applies to.
- Treating the estimated annual interest as an exact bill instead of a simple rate × balance snapshot.
- Forgetting that new charges, fees, minimum-payment formulas, and variable rates can change the real cost.
Related tools and guides
Estimate payoff time with the credit card payoff calculator, compare promotional-rate tradeoffs with the balance transfer calculator, or read how to compare loans for broader borrowing-cost context.
FAQ
Is weighted average interest rate the same as APR?
No. APR usually describes one account or offer. A weighted average rate summarizes several balances and their entered rates into one blended estimate.
Can I include a zero-interest balance?
Yes. A 0% balance still increases the total balance and can lower the blended average, but promotional periods and deferred-interest rules are not modeled.
Does this calculate monthly payments?
No. It only calculates blended rate math and a simple annual interest snapshot. Use payoff or loan calculators for payment estimates.
Before you rely on a blended rate
Check whether each entered rate is fixed, variable, promotional, penalty, or tied to a specific purchase category. If real statements separate balances by APR bucket, enter the closest matching balance and rate pairs rather than averaging by account name alone.
For important decisions, compare this simplified estimate with account statements, loan agreements, disclosures, payoff letters, and any professional guidance that applies.