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All calculatorsMethodology

Weighted Average Interest Rate Calculator

Weight up to three nominal annual interest rates by entered balances. See the combined balance and a simple annual interest illustration.

Interactive calculator · Method WEIGHTEDINTEREST-1.0 · Last reviewed: 2026-10-05

Calculate your scenario

Weighted nominal annual rate (%) = Σ(principal × annual rate %) ÷ Σ(principal). Simple annual interest illustration = Σ(principal × rate/100), assuming all balances stay constant for one year.

Your inputs

Try an example

Default worked example. Edit the inputs to calculate your scenario.

Default worked example

Weighted nominal annual rate 7%
Combined entered balance $30,000.00
Simple annual interest illustration $2,100.00

Principal-weighted nominal rates produce 7%. With balances held constant for one year, the simple interest illustration is $2,100.00. This is not APR or a consolidation quote.

How to use the calculator

Enter each loan balance and its nominal annual interest rate. Keep all balances in one currency and use zero balance for an unused row. Read the weighted rate and constant-balance annual interest illustration separately.

What the result means

A $10,000 balance at 5% and $20,000 at 8% have a 7% weighted nominal annual rate. Constant balances would produce $2,100 simple annual interest. A consolidation rate needs the actual loan terms.

Formula and units

Weighted nominal annual rate (%) = Σ(principal × annual rate %) ÷ Σ(principal). Simple annual interest illustration = Σ(principal × rate/100), assuming all balances stay constant for one year. Aggregate unrounded products before rounding the final illustration to cents.

Worked examples

Two balances at 5% and 8%: Principal — row 1: 10000 USD; Rate — row 1: 5 % per year; Principal — row 2: 20000 USD; Rate — row 2: 8 % per year; Principal — row 3: 0 USD; Rate — row 3: 0 % per year.
Example result: Weighted nominal annual rate: 7%; Combined entered balance: $30,000.00; Simple annual interest illustration: $2,100.00.

Three balances including zero-interest debt: Principal — row 1: 5000 USD; Rate — row 1: 0 % per year; Principal — row 2: 15000 USD; Rate — row 2: 4 % per year; Principal — row 3: 10000 USD; Rate — row 3: 6 % per year.
Example result: Weighted nominal annual rate: 4%; Combined entered balance: $30,000.00; Simple annual interest illustration: $1,200.00.

Limitations and common mistakes

This is not APR, a consolidation offer, an amortization schedule or a payoff comparison. Loan fees, compounding, changing balances and product-specific rounding are excluded. In particular this tool does not apply the US federal consolidation loan one-eighth-percent rule.

A simple average of rates ignores balance size. APR includes other borrowing costs and must not be substituted for the nominal rates used here.

Sources and assumptions

Method WEIGHTEDINTEREST-1.0; last formula review 2026-10-05. Sources and their supported claims. Calculation methodology.

Consumer Financial Protection Bureau: Interest rate and APR describe different costs. CFPB explains that APR includes costs beyond the nominal interest rate; this tool only combines entered nominal rates.