How Much Interest Will $100K Earn in a HYSA?
TL;DR
At a 4.25% APY, $100,000 in a top HYSA earns approximately $4,340 in year one (assuming monthly compounding). Over 3 years, it earns ~$13,290 if the rate holds, ~$10,800 if rates drop to 3.50%, and ~$12,000 if you average out a typical cutting cycle. A 3-year MYGA at 5.30% locks ~$16,750 over the same window. The HYSA yield is variable; the MYGA yield is fixed.
The short answer
At a top HYSA rate of 4.25% APY (Marcus, Ally, Discover, Capital One 360 as of mid-2026), $100,000 earns approximately $4,340 in the first year if the rate holds steady all 12 months. That assumes monthly compounding, which is standard for HYSAs.
But the rate will not hold steady. HYSAs are variable, and the Fed funds rate moves. If you average a 3-year window during which the Fed cuts 100 bps, your actual 3-year interest on $100,000 lands closer to $11,800-$12,400, not the $13,290 you would get if rates were frozen.
Year-one math: $100,000 at various HYSA rates
| HYSA APY | Year-1 interest | 3-year interest (rate held) | 5-year interest (rate held) |
|---|---|---|---|
| 3.50% | $3,557 | $10,866 | $18,759 |
| 3.75% | $3,815 | $11,672 | $20,164 |
| 4.00% | $4,074 | $12,486 | $21,585 |
| 4.10% | $4,178 | $12,813 | $22,157 |
| 4.25% | $4,334 | $13,304 | $23,019 |
| 4.50% | $4,595 | $14,127 | $24,459 |
| 5.00% | $5,116 | $15,786 | $27,394 |
Numbers assume monthly compounding on a stable $100,000 balance with no deposits or withdrawals. Compounding is meaningful but not huge at these rates: at 4.25% APY, daily vs monthly vs annual compounding changes the year-one interest by less than $4.
The variable-rate reality
The frozen-rate columns above are useful for sizing the math, but they are misleading for any horizon over 12 months. Real-world HYSA balances earn the time-weighted average of whatever the rate path actually is.
Three realistic 3-year paths starting at today's 4.25% APY:
| Path | 3-yr blended APY | Approx. interest on $100K |
|---|---|---|
| Rates hold flat at 4.25% (no Fed action) | 4.25% | $13,300 |
| Fed cuts 100 bps over Year 1, then pauses | ~3.85% | $12,000 |
| Fed cuts 200 bps over Year 1, then pauses | ~3.45% | $10,700 |
| Fed cuts 100 bps then hikes 50 bps | ~3.95% | $12,310 |
Across the realistic scenarios, $100K in a HYSA earns roughly $10,700-$13,300 over 3 years — a band of about $2,600. The middle of that band is the "expected value" if you have no rate view.
Compare: 3-year CD and 3-year MYGA
Same $100K, same 3-year horizon, locked-rate products:
| Product | Indicative APY | 3-yr interest | Tax treatment |
|---|---|---|---|
| HYSA (variable, midcase) | ~3.85% | ~$12,000 | Annual 1099-INT |
| 3-year bank CD (locked) | 4.30% | ~$13,470 | Annual 1099-INT |
| 3-year MYGA (A-rated, locked) | 5.30% | ~$16,750 | Deferred to withdrawal |
The CD beats the HYSA midcase by ~$1,470. The MYGA beats the HYSA midcase by ~$4,750 before tax-deferral compounding. In a 24% bracket, the MYGA's tax-deferral edge over the HYSA (which pays tax annually) adds roughly $700-$900 of additional after-tax value over the 3-year window.
What tax does to your real earnings
HYSA interest is taxed as ordinary income at your marginal federal rate (and state rate, if you live in a state with income tax). $4,340 of HYSA interest in a 24% federal + 9.3% CA bracket means $1,447 to taxes — $2,893 take-home, an effective after-tax yield of 2.89% on $100,000.
A non-qualified MYGA defers all that tax until you withdraw. If you hold for 3+ years and the deferral compounds, the effective after-tax yield gap widens beyond the headline APY spread.
When the answer changes
The HYSA earnings math is sensitive to four variables:
- Bank pass-through ratio. Aggressive online banks pass through 75-90% of Fed moves; legacy banks pass through 5-20%. If you bank at Chase or BofA, your HYSA might be earning 0.50% APY, not 4.25%. Check.
- Your tax bracket. Higher brackets favor tax-deferred MYGAs over taxable HYSAs.
- Your state. CA, NY, OR, MN savers pay state tax on HYSA interest; Treasury bills are exempt from state tax, which adds 50-100 bps of effective after-tax yield in those states.
- Promo rates. Some banks pay 5.00%+ as a 6-month introductory rate, then drop to 3.50% or lower. Read the small print on any HYSA paying meaningfully above the market average.
Common mistakes
- Quoting the headline APY as a 5-year return. A HYSA's headline APY is a 1-year forward projection of the current daily rate. It does not lock in a 5-year return.
- Ignoring monthly compounding. Banks usually compound monthly but quote APY (which already includes compounding). Do not double-count.
- Holding $100K+ at a big-bank low-yield HYSA. Chase Premier Savings pays around 0.02% APY in 2026. That is $20 per year on $100K. Moving to a top HYSA is the single highest-yield move most savers can make.
- Forgetting FDIC limits. $250K per depositor per bank per ownership category. A $300K balance in one HYSA is uninsured above $250K. Split across banks or use a sweep network.
What to do next
If your $100,000 is currently in a HYSA earning under 3.50% APY, the highest-ROI move is to switch to a top-tier online HYSA (Marcus, Ally, Discover, Capital One 360) earning ~4.20-4.30%. Takes 15 minutes to open, 2-3 business days to fund.
If you already have $100,000 in a top HYSA and your horizon is 3+ years, the next-highest-ROI move is to compare against a 3-year MYGA. The locked 5.30% rate plus tax deferral often wins by $3,000-$5,000 over a typical 3-year cutting cycle. See HYSA vs MYGA for 3-year money and how much $250K earns.
Frequently asked follow-up questions
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Disclosure
This article reflects publicly available HYSA, CD, and annuity rate information approximate to the date above. High-yield savings rates are variable and change frequently — often weekly. Always confirm current rates directly with the institution before opening or transferring. This is general educational content, not a personalized recommendation, solicitation, or offer of any specific product. Hans Goldstein is an independent licensed insurance producer (NPN 20602398) appointed with multiple A-rated carriers in the fixed-annuity market; Goldstein & Co. LLC is not a bank, broker-dealer, or registered investment adviser. HYSAs and CDs are deposit products of FDIC-insured banks or NCUA-insured credit unions; MYGAs and other annuities are insurance contracts backed by the issuing carrier and state guaranty associations. FDIC and NCUA insurance limits are typically $250,000 per depositor per institution per ownership category. Tax discussion reflects federal law as of 2026 and is subject to change; consult a tax professional for your situation.