The 30 day yield is the annualized rate of return a mutual fund or ETF generates from interest, dividends, and capital gains over a 30-day period. It reflects income earned during that time, scaled to a yearly rate for easy comparison across funds.
This metric appears on fund fact sheets and financial websites. It's not a guarantee of future returns. Instead, it shows what income the fund produced in the past month, adjusted to a 12-month basis using compounding math. For example, a 30 day yield of 3.2% means the fund would generate roughly 3.2% annual income if current earnings continued unchanged.
Regulated under SEC Rule 2a-7, the 30 day yield must be calculated using the most recent 30 days of income and the fund's net asset value (NAV) on the last day of the period. This ensures consistency across funds and prevents manipulation. The calculation excludes capital gains and focuses purely on income.
The 30 day yield uses a compound interest formula based on daily income. The fund's total income over 30 days is divided by the average NAV during that period. That result is then annualized using the formula: (1 + daily return)^365 − 1. The result is rounded to two decimal places.
For example, a money market fund earns $0.0083 in income per share over 30 days. Its average NAV was $1.00. The daily return is $0.0083 ÷ 30 = $0.000277. Annualizing: (1 + 0.000277)^365 − 1 = 0.1053, or 10.53%. But since the fund pays out income monthly, the actual 30 day yield reported is 3.2%, reflecting the net income earned and distributed.
Income includes interest from bonds, dividends from stocks, and fees. Capital appreciation is excluded. This keeps the yield focused on cash flow, not price changes. A fund with high volatility may have a stable 30 day yield if it holds low-risk securities.
The 30 day yield is derived from three core inputs: total income earned, average net asset value (NAV), and the number of days in the period. All values come from the fund's daily accounting records.
Income sources include:
These are summed over 30 days. The average NAV is computed by adding the NAV at the start and end of the period, dividing by two. The formula is:
30 Day Yield = (Total Income / Average NAV) × (365 / 30)After calculating, the result is rounded to two decimal places. The SEC requires this standardization so investors can compare yields across funds regardless of size or structure.
Investors use the 30 day yield to evaluate income-generating funds such as bond funds, money market funds, and dividend-focused ETFs. It helps compare which funds deliver higher passive income.
For example, two bond funds both report a 30 day yield of 4.1%. Fund A holds mostly short-term Treasuries. Fund B owns long-term corporate bonds. Both have similar yields, but Fund B likely carries higher credit risk. The yield alone doesn't reveal risk-but it signals income potential.
Financial platforms like Morningstar and Bloomberg display the 30 day yield alongside other metrics. It's updated daily and published weekly in fund prospectuses. Investors use it to assess whether a fund meets their income goals.
Many mistake the 30 day yield for total return. Total return includes both income and price changes. A fund with a 30 day yield of 3.5% could lose 2% in value over the same period. The yield shows income only.
Another error is assuming the yield equals the actual payout. Some funds distribute income monthly. The 30 day yield is a snapshot of performance, not a promise of future payments. A fund's yield can drop sharply if interest rates fall or if a bond defaults.
A lesser-known fact: the 30 day yield is not the same as the SEC yield. The SEC yield is a standardized version used in fund advertisements. It's calculated using the same formula but applies to a different set of rules. The SEC yield is often lower because it accounts for fees and expenses more strictly.
In May 2023, the iShares Core U.S. Aggregate Bond ETF (AGG) had a 30 day yield of 4.32%. Over the prior 30 days, the fund earned $0.0112 per share in interest. The average NAV was $102.45. Using the formula:
The daily income was $0.0112 ÷ 30 = $0.000373. Annualized: (1 + 0.000373)^365 − 1 = 0.1447, or 14.47%. But the actual 30 day yield is 4.32% due to the way income is reported and distributed.
The difference arises because the yield is based on net income after fees and taxes. AGG's expense ratio is 0.04%, reducing the effective yield. The 4.32% figure reflects what investors actually receive after costs.
When comparing funds, always check the 30 day yield alongside the expense ratio and credit quality. A fund with a 4.5% yield but a 1.2% expense ratio may pay less than one with a 4.0% yield and a 0.1% fee.
| Yield Type | Timeframe | Includes Price Changes? | Use Case |
|---|---|---|---|
| 30 Day Yield | 30 days | No | Compare income performance across funds |
| SEC Yield | 30 days | No | Standardized measure for advertising |
| Total Return | 12 months | Yes | Assess performance including price swings |
| Current Yield | Annual | No | Quick estimate for bond income based on price |
Understanding the 30 day yield helps avoid misleading comparisons. Always cross-check with the fund's prospectus and recent performance reports.
For investors tracking income streams, the 30 day yield offers a consistent benchmark. It's not perfect-market conditions change quickly-but it provides a clear, regulated view of what a fund has earned in the past month.