# Weighted Average Maturity (WAM): Definition, Formula, and Why It Matters for Bond Investors Published: 2026-01-07 Author: Warren Team URL: https://www.heywarren.com/blog/weighted-average-maturity --- A bond fund holding 50 different bonds of different maturities can't be described by a single maturity date. Weighted average maturity solves this, it gives you a single number that captures the average time until all the fund's bonds mature, weighted by their relative sizes. WAM is one of the most important metrics for fixed income investors assessing interest rate risk and duration exposure. ## What Is Weighted Average Maturity? Weighted average maturity (WAM) is the weighted mean of the maturities of the individual bonds in a portfolio or fund, where each bond's maturity is weighted by its market value (or face value) as a proportion of the total portfolio. WAM is reported by: - **Bond mutual funds and ETFs**: Summary of the portfolio's maturity profile - **Money market funds**: Regulatory metric, SEC rules restrict WAM for money market funds - **Mortgage-backed securities**: Time until principal is expected to be repaid (also called "weighted average loan age" for MBS) - **Municipal bond funds**: Indicating average exposure to long-term vs. short-term munis ## WAM Formula **WAM = Σ (Weight_i × Maturity_i)** ![Three-step process for calculating weighted average maturity from a bond portfolio.](data:image/svg+xml,%3Csvg%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%22%20viewBox%3D%220%200%20660%20125%22%20width%3D%22660%22%20height%3D%22125%22%20role%3D%22img%22%3E%3Ctitle%3EFlow%20diagram%3C%2Ftitle%3E%3Crect%20width%3D%22100%25%22%20height%3D%22100%25%22%20fill%3D%22%23f8fafc%22%2F%3E%3Crect%20x%3D%2230%22%20y%3D%2225%22%20width%3D%22170%22%20height%3D%2275%22%20rx%3D%2210%22%20fill%3D%22white%22%20stroke%3D%22%232563eb%22%20stroke-width%3D%222%22%2F%3E%3Ctext%20x%3D%22115%22%20y%3D%2258.5%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2214%22%20font-weight%3D%22600%22%20fill%3D%22%230f172a%22%3EGet%20Market%20Values%3C%2Ftext%3E%3Ctext%20x%3D%22115%22%20y%3D%2278.5%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2211%22%20fill%3D%22%2364748b%22%3EEach%20bond%26%2339%3Bs%20weight%3C%2Ftext%3E%3Cline%20x1%3D%22205%22%20y1%3D%2262.5%22%20x2%3D%22237%22%20y2%3D%2262.5%22%20stroke%3D%22%2364748b%22%20stroke-width%3D%222%22%2F%3E%3Cpolygon%20points%3D%22244%2C62.5%20235%2C57.5%20235%2C67.5%22%20fill%3D%22%2364748b%22%2F%3E%3Crect%20x%3D%22245%22%20y%3D%2225%22%20width%3D%22170%22%20height%3D%2275%22%20rx%3D%2210%22%20fill%3D%22white%22%20stroke%3D%22%232563eb%22%20stroke-width%3D%222%22%2F%3E%3Ctext%20x%3D%22330%22%20y%3D%2258.5%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2214%22%20font-weight%3D%22600%22%20fill%3D%22%230f172a%22%3EMultiply%20Weights%3C%2Ftext%3E%3Ctext%20x%3D%22330%22%20y%3D%2278.5%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2211%22%20fill%3D%22%2364748b%22%3E%C3%97%20years%20to%20maturity%3C%2Ftext%3E%3Cline%20x1%3D%22420%22%20y1%3D%2262.5%22%20x2%3D%22452%22%20y2%3D%2262.5%22%20stroke%3D%22%2364748b%22%20stroke-width%3D%222%22%2F%3E%3Cpolygon%20points%3D%22459%2C62.5%20450%2C57.5%20450%2C67.5%22%20fill%3D%22%2364748b%22%2F%3E%3Crect%20x%3D%22460%22%20y%3D%2225%22%20width%3D%22170%22%20height%3D%2275%22%20rx%3D%2210%22%20fill%3D%22white%22%20stroke%3D%22%232563eb%22%20stroke-width%3D%222%22%2F%3E%3Ctext%20x%3D%22545%22%20y%3D%2258.5%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2214%22%20font-weight%3D%22600%22%20fill%3D%22%230f172a%22%3ESum%20Products%3C%2Ftext%3E%3Ctext%20x%3D%22545%22%20y%3D%2278.5%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2211%22%20fill%3D%22%2364748b%22%3E%3D%20WAM%20in%20years%3C%2Ftext%3E%3C%2Fsvg%3E) *Three-step process for calculating weighted average maturity from a bond portfolio.* Where: - **Weight_i** = (Market value of bond i) / (Total portfolio market value) - **Maturity_i** = Years to maturity of bond i - The sum (Σ) is taken across all bonds in the portfolio **Example**: | Bond | Market Value | Maturity (Years) | Weight | Weight × Maturity | |---|---|---|---|---| | Bond A | $200,000 | 2 | 0.20 | 0.40 | | Bond B | $300,000 | 5 | 0.30 | 1.50 | | Bond C | $500,000 | 10 | 0.50 | 5.00 | | **Total** | **$1,000,000** | | **1.00** | **6.90 years** | **WAM = 6.9 years** This portfolio behaves on average as if it held a single 6.9-year bond, from a maturity perspective. ## WAM vs. Duration WAM and duration are related but measure different things: | Metric | Measures | Accounts For Cash Flows? | Sensitivity To | |---|---|---|---| | WAM | Average time to principal repayment | No | Maturity profile | | Modified Duration | Price sensitivity to interest rates | Yes (coupon + principal) | Interest rate risk | | Effective Duration | Price sensitivity including options | Yes + embedded options | Rate sensitivity with optionality | **Duration is the superior interest rate risk metric** because it accounts for all cash flows (coupons plus principal), discounted by their timing. A 10-year [zero-coupon bond](/blog/zero-coupon-bond) has a duration of 10 years. A 10-year bond paying a 6% coupon has a duration of about 7.5 years, because coupons received earlier effectively shorten the time-weighting of cash flows. WAM tells you when your principal is coming back. Duration tells you how much your portfolio will change in value for a given change in interest rates. Despite this, WAM remains widely reported because it's simpler to calculate and communicate. A fund with WAM of 20 years has a very different risk profile than one with WAM of 2 years. ## WAM for Money Market Funds The [SEC's Rule 2a-7](https://www.sec.gov) governing money market funds imposes strict WAM limits: ![SEC limits money market WAM to 60 days versus years-long WAM typical of long-term bond funds.](data:image/svg+xml,%3Csvg%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%22%20viewBox%3D%220%200%20800%20210%22%20width%3D%22800%22%20height%3D%22210%22%20role%3D%22img%22%3E%3Ctitle%3EComparison%3C%2Ftitle%3E%3Crect%20width%3D%22100%25%22%20height%3D%22100%25%22%20fill%3D%22%23f8fafc%22%2F%3E%3Ctext%20x%3D%22230%22%20y%3D%2257.5%22%20text-anchor%3D%22end%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2214%22%20font-weight%3D%22600%22%20fill%3D%22%230f172a%22%3EMoney%20Market%20%28max%29%3C%2Ftext%3E%3Crect%20x%3D%22240%22%20y%3D%2225%22%20width%3D%227.397260273972602%22%20height%3D%2255%22%20rx%3D%226%22%20fill%3D%22%232563eb%22%2F%3E%3Ctext%20x%3D%22259.3972602739726%22%20y%3D%2257.5%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2214%22%20font-weight%3D%22700%22%20fill%3D%22%232563eb%22%3Edays60%3C%2Ftext%3E%3Ctext%20x%3D%22230%22%20y%3D%22152.5%22%20text-anchor%3D%22end%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2214%22%20font-weight%3D%22600%22%20fill%3D%22%230f172a%22%3ELong-Term%20Fund%3C%2Ftext%3E%3Crect%20x%3D%22240%22%20y%3D%22120%22%20width%3D%22450%22%20height%3D%2255%22%20rx%3D%226%22%20fill%3D%22%237c3aed%22%2F%3E%3Ctext%20x%3D%22702%22%20y%3D%22152.5%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2214%22%20font-weight%3D%22700%22%20fill%3D%22%237c3aed%22%3Edays3.6K%3C%2Ftext%3E%3C%2Fsvg%3E) *SEC limits money market WAM to 60 days versus years-long WAM typical of long-term bond funds.* - **Maximum WAM**: 60 days for money market funds - This restriction ensures that money market funds don't take excessive interest rate risk or credit risk by holding longer-maturity securities A money market fund with WAM of 45 days is positioned conservatively. A fund at the 59-day limit is positioned more aggressively for yield but with more rate sensitivity. During periods of rising interest rates, money market funds quickly reprice as short-term securities mature and are replaced with higher-yielding instruments, the low WAM enables this rapid adjustment. ## WAM for Mortgage-Backed Securities In the MBS market, WAM describes the weighted average remaining term to maturity of the underlying mortgage loans. It's calculated similarly but weighted by remaining loan balances. **Example**: A pool of 30-year mortgages originated 5 years ago has a WAM of approximately 25 years (the remaining loan terms). If borrowers prepay mortgages, WAM shortens faster than expected. This is closely related to **weighted average loan age (WALA)**, the average age of the loans in the pool, which is the complement: WAM + WALA ≈ Original loan term. MBS investors monitor WAM closely because: - Prepayment speeds affect WAM faster than expected → cash returned early but must be reinvested at potentially lower rates (prepayment risk) - Extensions (slower prepayments when rates rise) lengthen WAM → interest rate risk increases when you least want it (extension risk) ## How WAM Affects Portfolio Strategy ### Rising Rate Environments ![How WAM length interacts with rate direction to shape portfolio outcomes.](data:image/svg+xml,%3Csvg%20xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%22%20viewBox%3D%220%200%20720%20480%22%20width%3D%22720%22%20height%3D%22480%22%20role%3D%22img%22%3E%3Ctitle%3EQuadrant%20matrix%3C%2Ftitle%3E%3Crect%20width%3D%22100%25%22%20height%3D%22100%25%22%20fill%3D%22%23f8fafc%22%2F%3E%3Crect%20x%3D%2290%22%20y%3D%2225%22%20width%3D%22300%22%20height%3D%22190%22%20fill%3D%22%23dbeafe%22%2F%3E%3Crect%20x%3D%22390%22%20y%3D%2225%22%20width%3D%22300%22%20height%3D%22190%22%20fill%3D%22%23d1fae5%22%2F%3E%3Crect%20x%3D%2290%22%20y%3D%22215%22%20width%3D%22300%22%20height%3D%22190%22%20fill%3D%22%23ffedd5%22%2F%3E%3Crect%20x%3D%22390%22%20y%3D%22215%22%20width%3D%22300%22%20height%3D%22190%22%20fill%3D%22%23ede9fe%22%2F%3E%3Cline%20x1%3D%2290%22%20y1%3D%22215%22%20x2%3D%22690%22%20y2%3D%22215%22%20stroke%3D%22%2364748b%22%20stroke-width%3D%222%22%2F%3E%3Cline%20x1%3D%22390%22%20y1%3D%2225%22%20x2%3D%22390%22%20y2%3D%22405%22%20stroke%3D%22%2364748b%22%20stroke-width%3D%222%22%2F%3E%3Ctext%20x%3D%22240%22%20y%3D%22100%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2213%22%20font-weight%3D%22700%22%20fill%3D%22%230f172a%22%3ESuboptimal%3C%2Ftext%3E%3Ctext%20x%3D%22240%22%20y%3D%22120%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2210%22%20fill%3D%22%2364748b%22%3E%E2%80%A2%20Misses%20price%20gains%3C%2Ftext%3E%3Ctext%20x%3D%22240%22%20y%3D%22136%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2210%22%20fill%3D%22%2364748b%22%3E%E2%80%A2%20Reinvests%20at%20lower%20rates%3C%2Ftext%3E%3Ctext%20x%3D%22540%22%20y%3D%22100%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2213%22%20font-weight%3D%22700%22%20fill%3D%22%230f172a%22%3EIdeal%3C%2Ftext%3E%3Ctext%20x%3D%22540%22%20y%3D%22120%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2210%22%20fill%3D%22%2364748b%22%3E%E2%80%A2%20Locks%20in%20high%20yields%3C%2Ftext%3E%3Ctext%20x%3D%22540%22%20y%3D%22136%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2210%22%20fill%3D%22%2364748b%22%3E%E2%80%A2%20Max%20price%20appreciation%3C%2Ftext%3E%3Ctext%20x%3D%22240%22%20y%3D%22290%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2213%22%20font-weight%3D%22700%22%20fill%3D%22%230f172a%22%3EIdeal%3C%2Ftext%3E%3Ctext%20x%3D%22240%22%20y%3D%22310%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2210%22%20fill%3D%22%2364748b%22%3E%E2%80%A2%20Reinvests%20higher%20quickly%3C%2Ftext%3E%3Ctext%20x%3D%22240%22%20y%3D%22326%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2210%22%20fill%3D%22%2364748b%22%3E%E2%80%A2%20Minimal%20price%20loss%3C%2Ftext%3E%3Ctext%20x%3D%22540%22%20y%3D%22290%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2213%22%20font-weight%3D%22700%22%20fill%3D%22%230f172a%22%3ESuboptimal%3C%2Ftext%3E%3Ctext%20x%3D%22540%22%20y%3D%22310%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2210%22%20fill%3D%22%2364748b%22%3E%E2%80%A2%20Slow%20to%20reprice%3C%2Ftext%3E%3Ctext%20x%3D%22540%22%20y%3D%22326%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2210%22%20fill%3D%22%2364748b%22%3E%E2%80%A2%20Larger%20price%20declines%3C%2Ftext%3E%3Ctext%20x%3D%2290%22%20y%3D%22425%22%20text-anchor%3D%22start%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2211%22%20fill%3D%22%2364748b%22%3EShort%20WAM%3C%2Ftext%3E%3Ctext%20x%3D%22690%22%20y%3D%22425%22%20text-anchor%3D%22end%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2211%22%20fill%3D%22%2364748b%22%3ELong%20WAM%3C%2Ftext%3E%3Ctext%20x%3D%22390%22%20y%3D%22453%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2212%22%20font-weight%3D%22600%22%20fill%3D%22%230f172a%22%3EPortfolio%20WAM%3C%2Ftext%3E%3Ctext%20x%3D%2280%22%20y%3D%2237%22%20text-anchor%3D%22end%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2211%22%20fill%3D%22%2364748b%22%3ERising%20Rates%3C%2Ftext%3E%3Ctext%20x%3D%2280%22%20y%3D%22405%22%20text-anchor%3D%22end%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2211%22%20fill%3D%22%2364748b%22%3EFalling%20Rates%3C%2Ftext%3E%3Ctext%20x%3D%2235%22%20y%3D%22215%22%20text-anchor%3D%22middle%22%20font-family%3D%22system-ui%2C-apple-system%2Csans-serif%22%20font-size%3D%2212%22%20font-weight%3D%22600%22%20fill%3D%22%230f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*How WAM length interacts with rate direction to shape portfolio outcomes.* In a rising interest rate environment, shorter WAM is desirable: - Short-maturity bonds mature quickly and proceeds can be reinvested at higher rates - Price declines are smaller for shorter-maturity bonds - A fund with WAM of 2 years adjusts to higher rates much faster than one with WAM of 15 years ### Falling Rate Environments In a falling interest rate environment, longer WAM is advantageous: - Long-maturity bonds lock in higher yields for longer - Price appreciation is larger for long-maturity bonds - A fund with WAM of 20 years benefits most from a sustained rate decline ### Laddered Bond Portfolios A **bond ladder**, holding bonds maturing at regular intervals, maintains a moderate, stable WAM over time. As short-term bonds mature and proceeds are reinvested at the long end, the WAM stays roughly constant, providing both reinvestment at current rates and locked-in longer-term yields. ## Reading WAM in Fund Fact Sheets When evaluating a bond fund, WAM is typically listed in the fund's fact sheet or Morningstar profile. Key ranges: | WAM Range | Category | Rate Risk | |---|---|---| | < 1 year | Ultra-short / money market | Very low | | 1–3.5 years | Short-term | Low | | 3.5–6 years | Intermediate-term | Moderate | | 6–10 years | Intermediate-long | Elevated | | > 10 years | Long-term | High | For individual investors building a fixed income portfolio, matching WAM to your investment horizon and interest rate outlook is a key portfolio management decision. ## Weighted Average Life (WAL): A Related Concept Weighted average life (WAL) is similar to WAM but focuses specifically on when principal payments are received, accounting for amortization schedules. For bonds with periodic principal payments (like mortgages or amortizing loans), WAL is shorter than WAM. For standard bullet bonds (principal paid at maturity), WAL equals WAM. For amortizing bonds, WAL < WAM. ## Conclusion Weighted average maturity is a straightforward but essential fixed income metric that tells you, in a single number, when you can expect your bond portfolio's principal to be returned. It's a key input for interest rate risk assessment, and the regulatory backbone of money market fund stability. For investors building bond portfolios, tracking your portfolio's WAM relative to your time horizon and interest rate views helps you manage exposure effectively. For related fixed income concepts, see our guides on [accrued interest](/blog/accrued-interest), [Cox-Ingersoll-Ross model](/blog/cox-ingersoll-ross), and [netting in finance](/blog/netting-in-finance). Warren at [heywarren.com](https://heywarren.com) helps you analyze your fixed income portfolio's interest rate risk with clear, actionable guidance. --- ## Related Reading **More from Warren**: - [A Bond Is Issued at Par Value When: Understanding Par, Premium, and Discount Bonds](/blog/bond-issued-at-par) - [Bearer Bonds: What They Were, Why They Disappeared, and Their Legacy](/blog/bearer-bonds) - [Accrued Interest: What It Is, How to Calculate It, and Why It Matters for Bond Investors](/blog/accrued-interest) **Authoritative sources**: - [TreasuryDirect, Bonds and Securities](https://www.treasurydirect.gov/marketable-securities/) - [SEC, Bonds](https://www.investor.gov/introduction-investing/investing-basics/investment-products/bonds-or-fixed-income-products/bonds) - [FINRA, Bond Basics](https://www.finra.org/investors/learn-to-invest/types-investments/bonds)