APY Calculator — South Dakota 2026
Convert APR to APY for savings accounts and CDs as a South Dakota resident. South Dakota has no state income tax — your interest income is only taxed at the federal level.
Quick Answer
A 4.5% APR compounded monthly has an effective APY of 4.5941%. Compounded daily: 4.6028% APY. As a South Dakota resident with no state income tax, your savings interest is only subject to federal income tax (10%–37%). Always compare savings accounts using APY — it accounts for compounding.
What do you want to calculate?
Convert APR to APY
The stated interest rate before compounding
Results
APY (Effective Annual Yield)
4.5940%
vs 4.5% APR stated rate
Annual Earnings on $10,000
$459.40
Compounding Boost
+0.0940%
APY minus APR
A 4.5% APR compounded monthly has an effective APY of 4.5940%. The difference of 0.0940% is worth $9.40 per year on a $10,000 balance.
APR vs APY — Common Rate Comparisons
| APR | APY (Daily) | APY (Monthly) | APY (Quarterly) |
|---|---|---|---|
| 3.00% | 3.0453% | 3.0416% | 3.0339% |
| 3.50% | 3.5618% | 3.5567% | 3.5462% |
| 4.00% | 4.0808% | 4.0742% | 4.0604% |
| 4.50% | 4.6025% | 4.5940% | 4.5765% |
| 5.00% | 5.1267% | 5.1162% | 5.0945% |
| 5.50% | 5.6536% | 5.6408% | 5.6145% |
APY FAQs — South Dakota
How is APY interest taxed in South Dakota?
Interest earned on savings accounts and CDs (whether a high APY or low APY) is taxed as ordinary income. South Dakota has no state income tax, so interest income is only subject to federal income tax (10%–37% based on your bracket). This gives South Dakota residents a meaningful advantage over residents of high-tax states.
What is the best APY savings account in South Dakota?
APY rates are set by banks and credit unions nationally — they don't vary by state. As of 2026, the best APYs for South Dakota residents are available at online banks and credit unions offering 4.0%–5.5% APY. You don't need to bank locally to access the best rates — any FDIC-insured online bank accessible from South Dakota qualifies. Compare using APY, not APR, since APY accounts for compounding.
Is there a state tax on savings account interest in South Dakota?
No — South Dakota does not have a state income tax. Interest earned on savings accounts, CDs, and money market accounts is only subject to federal income tax in South Dakota.
Should I use a savings account or CD for better APY in South Dakota?
Both are taxed identically in South Dakota — as ordinary income. The choice comes down to liquidity needs: savings accounts allow unlimited deposits and withdrawals (though federal rules allow up to 6 per month before fees), while CDs lock in your rate for a fixed term with an early withdrawal penalty. If rates are expected to fall, a CD locks in today's higher APY. If rates may rise, a savings account lets you benefit from increases. In South Dakota with no state tax, both options benefit from the same tax-free-from-state-tax advantage.
What is APY vs APR for a South Dakota savings account?
APR is the stated interest rate before compounding; APY is the effective annual return after compounding. Federal law (Truth in Savings Act) requires all banks, including those serving South Dakota residents, to disclose APY. Always compare using APY. A 4.5% APR compounded daily has a 4.603% APY — a 4.5% APR compounded monthly has a 4.594% APY. The difference is small but meaningful on large balances. $100,000 at 4.5% APR daily compounding earns $4,603/year vs $4,500 with annual compounding.