The question
"I know I need an emergency fund. How big should it be, and where should the money actually sit?"
The idea
- An emergency fund is money set aside for a surprise: a lost job, a car repair, a medical bill. Its one job is to be there, in full, on the day you need it. A return is a bonus.
- So you want three things from its home, in this order:Its value doesn't fall when you need to take it out.You can reach it within days.It earns something while it waits.
- A common size is 3 to 6 months of needs: the rent, food, bills and debt payments from the budget in Where your money goes. With needs of $2,000 a month, that is $6,000 to $12,000.
Worked example
Take $12,000 and four ETFs it could sit in. All numbers cover the year Nov 10, 2025 to Nov 10, 2026.
- BIL holds Treasury bills that mature (are paid back) in 1 to 3 months.
- JPST is an ultrashort fund: mostly loans maturing within 3 years, including loans to companies.
- SHY holds US Treasury bonds maturing in 1 to 3 years.
- AGG holds a broad mix of US bonds, with 30.9% maturing in over 20 years.
The 12-month yield is the cash a fund paid over the year, as a share of its price a year ago. Total return (Cash or invested) adds the price change to that cash.
| Fund | 12-month yield | Total return | $12,000 earned |
|---|---|---|---|
| BIL | 3.7% | +3.67% | $440 |
| JPST | 4.1% | +3.50% | $420 |
| SHY | 3.5% | +1.77% | $213 |
| AGG | 4.0% | −0.32% | −$39 |
Step 1. Earned = $12,000 × total return. For SHY: $12,000 × 1.77% = $213.
Step 2. Compare yield with total return. BIL's two match: its price barely moved. AGG paid 4.0% but returned −0.3%, so its price fell by roughly the difference. SHY's price fell 1.8%, which took its 3.5% yield down to a 1.8% return.
Step 3. For scale: in the month to Nov 10, 2026, SPY, an S&P 500 fund, fell 3.7%, about $442 on $12,000. Stocks are a poor home for money with a job this short.
The longer a fund's loans run, the more its price can move (Bonds for income shows why). Short Treasury bills barely move.
The common mistake
"Pick the highest yield." This year, AGG's 4.0% yield returned less than BIL's 3.7%, because AGG's price fell.
Now check each fund's worst fall (Your first fund check). Over each fund's full ETFIQ scorecard (the windows differ), BIL's was 0.4% (January 2010 to November 2026), JPST's 3.2% (May 2017 to November 2026) and AGG's 18.2% (July 2011 to November 2026). An emergency fund can't afford an 18% fall.
Check your understanding
Pick an answer to see why. Two of three right passes the lesson.
1. What is the first job of an emergency fund?Answer: A. Be there, in full, when you need it. a surprise bill can come in any month, so the value matters more than the return. Not B: a higher return usually comes with prices that can fall.2. Over the year to Nov 10, 2026, how much did $12,000 in SHY earn?Answer: D. About $213. $12,000 × 1.77% total return = $213. Not A: the yield leaves out SHY's 1.8% price fall.3. Dee needs $3,000 a month and wants 4 months covered. Fund X yields 5% and holds 20-year bonds. Fund Y yields 3.7% and holds 3-month Treasury bills. Which fact matters most?Answer: C. Fund X's long bonds can fall in price, so the $12,000 might not be there in full. long loans swing in price, and an emergency fund can't wait for a recovery. Not A: the extra 1.3 points of yield is about $156 a year on $12,000; a price fall can cost far more.
Takeaways
- Size it first: 3 to 6 months of needs.
- Hold it where the value barely moves.
- Judge a cash-like fund by total return and its worst fall, not by yield alone.