How this instrument works
A fund's stated yield is a starting quote, not a forecast of account growth. Compounding lifts it first — interest credited more than once a year earns interest on itself before the year is out — and an ongoing expense ratio then pulls a flat slice back out, since a fund's operating cost is deducted from assets whether the year was strong or flat. Effective annual yield after fees is what remains once both adjustments are made: the number that actually tracks what a dollar left in the fund becomes over twelve months.
The formula runs in two stages on purpose. First, (1 + i ⁄ n)ⁿ − 1 compounds the stated rate n times a year, the same mechanics behind any interest-bearing account — more frequent crediting always pushes the result up, though by a shrinking amount as n grows large. Second, the expense ratio is subtracted as a flat percentage-point charge after that compounding is finished, not folded into the rate before it compounds. That is a simplification: a fund's real daily fee accrual shaves a hair off the balance being compounded, not off the final answer, so a mathematically exact net figure runs a touch below what a flat subtraction shows at high stated yields — the gap stays small at the expense ratios most funds actually charge, under one percent, but it is not zero.
Retail investors screening money market funds, short-duration bond funds, or a cash sweep account against each other reach for this figure because two funds rarely share both a compounding convention and a cost structure, so comparing headline yields side by side compares incompatible numbers. The mistake this catches is trusting a fund's marketing rate as the figure that will show up in a statement: a fund advertising the highest stated yield in a comparison table can still finish behind a lower-quoted competitor once its expense ratio outweighs the gap that compounding bought it.
- Enter the headline rate into Stated annual yield, % — the quote from the fund's fact sheet, not yet adjusted for anything.
- Set Compounding to how often the fund credits interest: Annually, Semi-annually, Quarterly, Monthly, or Daily.
- Enter Annual expense ratio / fee drag, % — the fund's ongoing yearly operating cost, taken from its prospectus.
- Read Effective annual yield after fees, % — the compounded rate with that cost already subtracted.
- Hold the stated yield fixed and change only Compounding or the fee to see which one moves the net figure more.
Worked example — 5% stated, monthly, 0.5% fee
A money market fund quotes a 5% stated annual yield and credits interest monthly, so Stated annual yield, % is set to 5 and Compounding to Monthly, making n equal 12. Before any cost, monthly crediting compounds that 5% up to 5.116190% for the year — twelve small monthly credits, each earning a sliver of interest on interest already added the month before.
The fund also charges a 0.5% annual expense ratio, entered in Annual expense ratio / fee drag, %. Subtracting that flat 0.5 from 5.116190% leaves Effective annual yield after fees, % reading 4.616190 — close to 4.62% once rounded, roughly ten basis points below what compounding alone would suggest, and the figure that actually sets how fast a balance left in the fund grows over the year.
Questions
Why subtract the expense ratio instead of compounding it in?
Because that is the simpler, faster comparison this instrument is built for: it treats the expense ratio as a flat charge against the already-compounded rate, rather than a drag folded into every period before compounding runs. The two approaches land close together at the expense ratios most fund investors see, under 1% a year, so the flat subtraction is a fair approximation, not a mathematically exact fee model.
How is this different from a bank's advertised APY?
A bank's APY under Regulation DD is pure compounding math on a nominal rate — no cost is subtracted, because deposit accounts rarely carry a separate ongoing fee. This instrument adds a second step banks don't need: a fund's expense ratio, an annual cost real funds actually charge, removed after the compounding step so the result reflects what an investor keeps, not just what compounding alone produces.
Who actually reaches for a number like this?
Retail investors and advisors screening money market funds, short-duration bond funds, or cash-alternative products against each other, where each option quotes a different stated yield on a different compounding schedule and carries a different cost. One net figure lets those choices sit on the same axis instead of comparing a monthly-compounding, low-fee fund against a daily-compounding, higher-fee one by eye.
What is the most common mistake this figure catches?
Ranking funds by their stated yield alone. A fund quoting the highest headline rate in a comparison table can still finish last once its expense ratio outweighs whatever its compounding schedule gained — this figure surfaces that reversal before money moves, instead of after a year of statements confirms it.
Does this figure include taxes or a sales load?
No. It nets out only the ongoing expense ratio entered in the fee field. A front-end sales load charged at purchase, a back-end redemption fee, and any tax owed on interest or distributions sit outside this arithmetic — each depends on the account type and the investor's own tax situation, so add or subtract them separately once this net yield is in hand.
Why does raising Compounding from Annually to Daily only help a little?
Because compounding has a ceiling. As crediting periods multiply, (1 + i ⁄ n)ⁿ climbs toward eⁱ and stops moving much once n passes about 12; at a 5% stated yield, Daily gains roughly one hundredth of a percentage point over Monthly. A lower expense ratio usually moves the net figure far more than switching compounding frequency does.
References
- SEC investor.gov — How Fees and Expenses Affect Your Investment Portfolio
- Federal Reserve — Selected Interest Rates (H.15)
Read this first: This instrument shows arithmetic, not advice. Real offers add fees, taxes and terms that vary by lender and place — verify the figures against your actual paperwork before deciding anything.