Blended (Weighted Average) Interest Rate Calculator
Combine several debts at different balances and rates into a single weighted-average effective rate.
Input Data
Results
At a glance:The Blended Rate calculator combines several debts at different balances and rates into one weighted-average effective rate. Formula: blended rate = sum(balance_i x rate_i) / sum(balance_i). The result leans toward the larger, heavier balance. WARNING: It is a weighted average, not the rate of any consolidation loan you could actually obtain; it ignores fees, terms and availability. Use it to decide which large high-rate debt to clear first, or whether a lower-rate consolidation loan is worthwhile.
Formula
Blended rate = total annual interest / total loan balance.
Weighted rate = Σ (balance_i × rate_i) / Σ balance_i.
$$$r_{blended}=\\dfrac{\\sum_{i}(B_i\\times r_i)}{\\sum_{i}B_i}$$$$$$B_i$ $i$ $r_i$$$$$$\\dfrac{2000\\times2\\%+3000\\times4\\%+200\\times3\\%}{2000+3000+200}=\\dfrac{166}{5200}\\approx3.192\\%$$$How to Use
- Enter the balance and annual rate of each debt (up to three).
- View the blended rate and the total balance.
- Use the result to compare against a potential consolidation loan rate.
Case Studies
Case 1: The effective rate after a mortgage top-up (blend-and-extend)
Mr Chan has an outstanding mortgage of HK$2,000,000 at 2%. He tops up HK$500,000 for renovation at 5%, blended into the original mortgage by the bank.
Blended rate = (2,000,000 x 2% + 500,000 x 5%) / 2,500,000 = 2.6%. Although the top-up rate is as high as 5%, the blended overall rate only edges up to 2.6% because the original mortgage is large and cheap — showing the true impact of the top-up, not just the scary 5%.
Case 2: Consolidating two credit cards into one effective rate
Ms Lee has card A: HK$30,000 at 30% and card B: HK$20,000 at 18%. She wants the overall weighted-average rate to judge a consolidation loan.
Blended rate = (30,000 x 30% + 20,000 x 18%) / 50,000 = 25.2%. Her HK$50,000 of card debt effectively costs 25.2%. If she can get a personal loan well below 25.2% (say 6-10%), consolidating would significantly cut interest. The blended rate turns two rates into one comparable number.
FAQ
What is a blended rate?
It is the weighted-average interest rate across several debts, weighted by each balance. It tells you the true overall cost of borrowing, not just the highest or lowest single rate.
Why does the blended rate lean toward the larger balance?
Because each rate is weighted by its balance, a large low-rate debt pulls the blended rate down, while a large high-rate debt pulls it up. A small high-rate debt barely moves the overall figure.
Does the blended rate equal a consolidation loan rate?
No. It is a weighted average for comparison only. Whether you can actually consolidate at a lower rate depends on the loan products available and their fees and terms.
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References
Content review: Calculatorism Finance Team. Results are for reference only; please refer to the relevant authorities for the official figures.