The weighted average interest rate of a loan portfolio is the sum of each loan’s current balance multiplied by its current interest rate, divided by the total current balance. Larger loans carry proportionally more weight, so the result is the portfolio’s actual blended cost of debt, which a simple average of the rates does not give. Most errors in the number come from the weights and the dates, not from the rates. A balance from last year or a floating rate from last quarter produces a figure that looks precise and describes no day in particular.
The weighted average interest rate formula
Weighted average rate = sum of (current balance × current rate) ÷ sum of current balances
The numerator is annual interest at today’s rates, so the formula reads more plainly as total annual interest divided by total debt. Each input needs a date: balances as of the same day, and floating rates on the same reset or observation date.
The metric is common enough to appear in securities rules. SEC Regulation S-X requires registrants to disclose, in a note, the weighted average interest rate on short-term borrowings outstanding at each balance sheet date. Freddie Mac’s securities disclosure guide reports two separate figures for the loans behind each security: the weighted average interest rate in effect when the security was issued and the one in effect during the current reporting period. That distinction, issuance versus current, is one internal calculations often miss.
A worked example across five loans
Illustrative example: a five-loan portfolio, floating rates all-in at an assumed SOFR of 3.75%
| Loan | Current balance | Rate | Type | Annual interest (balance × rate) |
|---|---|---|---|---|
| A, agency multifamily | $40,000,000 | 4.00% | Fixed | $1,600,000 |
| B, life company industrial | $25,000,000 | 5.50% | Fixed | $1,375,000 |
| C, bridge multifamily | $15,000,000 | 7.25% (SOFR + 3.50%) | Floating | $1,087,500 |
| D, bank office | $12,000,000 | 6.75% (SOFR + 3.00%) | Floating | $810,000 |
| E, bank retail | $8,000,000 | 6.00% | Fixed | $480,000 |
| Total | $100,000,000 | $5,352,500 |
Weighted average rate: $5,352,500 ÷ $100,000,000 = 5.3525%, or 5.35%.
The simple average of the five rates is (4.00 + 5.50 + 7.25 + 6.75 + 6.00) ÷ 5 = 5.90%. It overstates the cost of debt by 55 basis points because it gives the $8 million loan the same vote as the $40 million loan. Applied to $100 million, the simple average implies $5,900,000 of annual interest, $547,500 more than the portfolio actually pays.
Fixed and floating: blend them, then split them
A single blended rate hides the part of the portfolio that moves. Report the fixed and floating buckets separately, each weighted within itself.
Illustrative example: the same five loans split by rate type
| Bucket | Balance | Annual interest | Weighted rate | Share of debt |
|---|---|---|---|---|
| Fixed (A, B, E) | $73,000,000 | $3,455,000 | 4.73% | 73% |
| Floating (C, D) | $27,000,000 | $1,897,500 | 7.03% | 27% |
| Portfolio | $100,000,000 | $5,352,500 | 5.35% | 100% |
The floating bucket’s rate is a snapshot. Unhedged, a 100 basis point rise in SOFR adds $270,000 of annual interest (1% of $27,000,000) and lifts the portfolio rate to 5.62%. Hedges change that. If loan C carries a cap at a 4.00% SOFR strike, C’s rate net of the cap payout rises only 25 basis points, to a 7.50% ceiling, adding $37,500; D adds $120,000. The portfolio rate becomes $5,510,000 ÷ $100,000,000 = 5.51%. Floors work in the other direction when rates fall. A dashboard should show the rate gross and net of hedges; see caps in your debt portfolio. For a forward-looking figure, project each reset on the SOFR forward curve rather than holding today’s rate flat.
Weighted average maturity and DSCR
The weighted average interest rate is one of three portfolio figures that belong together.
Weighted average maturity (WAM) uses the same weights: sum of (balance × years to maturity) ÷ total balance. Suppose, as of the same date, A matures in 6.0 years, B in 3.5, C in 1.5, D in 2.0 and E in 4.0.
- Balance-weighted: (40 × 6.0 + 25 × 3.5 + 15 × 1.5 + 12 × 2.0 + 8 × 4.0) ÷ 100 = 406 ÷ 100 = 4.06 years.
- Simple average: (6.0 + 3.5 + 1.5 + 2.0 + 4.0) ÷ 5 = 3.4 years.
- If C has one 12-month extension and D has two, the fully extended figure is 445 ÷ 100 = 4.45 years.
Show initial and extended WAM side by side, because extensions are options with conditions. A WAM of four years can still hide a large maturity next year, so pair it with the ladder in the real estate debt schedule. Auditors look at the ladder too: US GAAP (ASC 470-10-50-1) requires aggregate principal maturities of long-term debt for each of the five years after the balance sheet date.
Weighted average DSCR weights each loan’s debt service coverage ratio by balance. With DSCRs of 1.80x, 1.45x, 1.10x, 1.30x and 1.60x on A to E, the balance-weighted figure is (40 × 1.80 + 25 × 1.45 + 15 × 1.10 + 12 × 1.30 + 8 × 1.60) ÷ 100 = 153.15 ÷ 100 = 1.53x. That comfortable number contains loan C at 1.10x. Use the weighted figure as a trend line and track covenants loan by loan, on each lender’s definition. See DSCR and debt yield tests with lender-specific adjustments. State the basis as well: Freddie Mac’s disclosure guide, for example, defines its weighted average DSCR at loan underwriting, which is a different number from DSCR on the latest trailing financials.
Common calculation mistakes
Weighting by original balance. Suppose loan A was originated at $50,000,000 and loan E at $10,000,000, and both have since amortized. Weighted by original amounts ($112,000,000 in total), the rate is $5,872,500 ÷ $112,000,000 = 5.24%, 11 basis points below the true 5.35%. The error grows as older loans pay down, and after a rising-rate cycle those are often the lower coupons.
Commitments instead of funded balances. A bridge or construction loan with future funding weighted at its full commitment overstates its influence until it is drawn.
Spread instead of all-in rate. Weighting “SOFR + 3.50%” as 3.50% understates the floating cost by the full index.
Mixed as-of dates. Balances from the last quarter end combined with floating rates from this month describe no single day.
Mixed daycounts. A 6.00% rate on an Actual/360 loan costs more per year than 6.00% on 30/360. Freddie Mac’s disclosure guide publishes a weighted average net rate converted from Actual/360 to 30/360 alongside the unconverted figure. Convert before blending, or blend actual interest dollars.
Mixed ownership bases. Joint venture loans at 100% in one blend and at the owner’s share in another. Choose one basis and label it.
What to track
- Weighted average rate, gross and net of hedges, with its as-of date.
- The same figure split into fixed and floating buckets.
- Sensitivity of the portfolio rate and annual interest to a 100 basis point move in the index.
- Weighted average maturity at initial and fully extended dates, beside the maturity ladder.
- Weighted average DSCR as a trend, with every loan’s covenant test tracked separately.
- The weighting basis in every report: current funded balance, stated ownership share, one daycount.
For owners reporting across several funds, the same calculations run at each level of the hierarchy. See loan portfolio management for private equity real estate funds.
How this looks in LoanBoss
LoanBoss unifies loan abstracts, accounting feeds and live rates to refresh DSCR, balances, rates, mark-to-market values and cash flows automatically, so the balances and rates behind a weighted figure are current rather than a quarterly copy. Each loan carries its own index, payment convention, daycount and business day adjustment, and hedges are valued with live rates. Teams send the reports they already use and LoanBoss rebuilds them in the platform so they stay live; see loan portfolio dashboards with real-time rates.
Frequently Asked Questions
How do you calculate a weighted average interest rate?
Multiply each loan’s current balance by its current rate, add the results, and divide by the total current balance. The answer equals total annual interest divided by total debt.
Why not take a simple average of the rates?
A simple average gives every loan the same weight regardless of size. In the example above it overstated the cost of debt by 55 basis points.
Should the weights be original or current balances?
Current funded balances. Original amounts overweight loans that have amortized and misstate the rate the portfolio pays today.
How should floating-rate loans enter the calculation?
At the all-in rate on a stated reset date, index plus spread, with floors applied. Show the result gross and net of caps and swaps.
What is weighted average maturity?
The balance-weighted average time to maturity across the portfolio. Report it at initial and fully extended maturities, alongside the maturity ladder.
Key takeaways
- Weighted average interest rate equals total annual interest at current rates divided by total current balance.
- A simple average of rates ignores loan size; in the example it overstated the cost of debt by 55 basis points.
- Split the figure into fixed and floating buckets and show floating exposure net of hedges.
- Weighted average maturity and weighted average DSCR use the same weights, and neither replaces the ladder or the loan-level covenant test.
- Most errors come from the inputs: original balances, commitments, spreads without the index, mixed dates and mixed daycounts.
Related reading
- Floating-rate re-amortization and SOFR tracking
- Automating the SREO and debt summary
- Portfolio cash flow projections and hold/sell scenarios
- Why Excel breaks for loan portfolios
- Floating rate and interest rate cap in the glossary
One rate for the whole portfolio is only as good as the balances and resets behind it. LoanBoss keeps both current.
Sources
- US Securities and Exchange Commission, Regulation S-X Rule 5-02, balance sheet disclosures (17 CFR 210.5-02)
- Freddie Mac, Disclosure Guide, Version 1.11, security level weighted average attributes (2025)
- FASB ASC 470-10-50-1, disclosure of long-term debt maturities, via Deloitte Accounting Research Tool, Roadmap: Debt, section 14.4 (2025)