Two people each have $10,000 in the bank. One earns $200 a year in interest, the other earns $30 — the entire difference comes down to knowing how to calculate deposit returns. Most people walk into a bank, ask "what's the rate?", sign, and only later realize they parked their money in the lowest-yielding product. Let's get this straight so you can compute every dollar yourself.
How to Read Deposit Rates: Don't Just Look at "1-Year"
When you check rates at a bank, don't fixate on the single "1-year" figure. Within the same bank, rates vary a lot by term, minimum balance, and product type. As a rough guide to typical quoted rates: checking accounts pay about 0.1%-0.2%, 3-month terms around 1.0%-1.2%, 6-month around 1.2%-1.4%, 1-year around 1.4%-1.7%, 2-year around 1.6%-1.9%, and 3-year around 1.9%-2.2%. Longer terms pay higher rates — that's the basic rule, though occasionally 3-year and 5-year rates "invert" (5-year pays less than 3-year) because banks don't want liabilities locked up that long.
Beyond term length, the minimum deposit also moves the rate. Ordinary time deposits can start at a few hundred dollars, while large-denomination certificates of deposit (CDs) usually require a $20,000 minimum — precisely because of that higher barrier, CD rates typically run 0.1-0.3 percentage points above regular deposits of the same term. There are also special products for specific groups, like pensioner editions or new-customer offers, which often pay more but usually have purchase limits.
How Deposit Interest Is Calculated: A Simple-Interest Formula
Deposits earn simple interest, and the formula is easy: Interest = Principal × Annual Rate × Years. At maturity the principal and interest come out together; interest does not compound.
Example: $10,000 in a 3-year deposit at 2.0% gives interest = 10,000 × 2.0% × 3 = $600. A 1-year deposit at 1.5% gives 10,000 × 1.5% × 1 = $150. Notice the difference: on the same $10,000, the 3-year term earns an average of $50 more per year than the 1-year term.
To quickly convert between daily, monthly, and annual figures, use the percentage calculator — plug in the rate and principal and it returns the interest per period. One trap: banks sometimes advertise "daily yield per $10,000." Convert that to an annual rate by multiplying by 365: a daily yield of $0.55 per $10,000 means 0.55 ÷ 10,000 × 365 ≈ 2.0% annual.
| Product | Principal | Annual rate | Term | Interest at maturity |
|---|---|---|---|---|
| Checking | $10,000 | 0.15% | 1 year | $15 |
| 1-year deposit | $10,000 | 1.5% | 1 year | $150 |
| 3-year deposit | $10,000 | 2.0% | 3 years | $600 |
| 3-year CD | $20,000 | 2.2% | 3 years | $1,320 |
Is the $20,000 CD Minimum Worth It?
A large-denomination certificate of deposit is a deposit product aimed at big balances, usually starting at $20,000, and it carries deposit insurance — just as safe as an ordinary time deposit. It beats a regular deposit in three ways. First, a higher rate: 3-year CDs often run 0.1-0.3 points above regular 3-year deposits. Second, transferability: if you need cash in a hurry, you can sell the CD to someone else instead of forfeiting all your interest. Third, some CDs pay interest monthly, giving you a steady income stream — handy for people living off interest.
But a CD is not risk-free. If you redeem before maturity, the bank typically pays only checking-account interest — buy a 3-year CD at 2.2%, cash out after 18 months, and your interest may drop from 2.2% to around 0.15%. That's a huge loss. Before locking into a CD, make sure you won't need the money for the full term.
Choosing a Term: Let Compounding Help You Decide
Picking a term isn't just about simple interest — think about compounding. Deposits themselves pay simple interest, but at maturity the principal plus interest can roll into a new deposit, letting interest earn interest. Two consecutive 3-year terms at 2.0% (6 years total) vs. six 1-year terms at 1.5%: the gap widens steadily. The compound interest calculator shows how your principal grows at different rates over time.
If you're not sure when you'll need the money, use the laddering strategy: split $30,000 into three CDs of $10,000 each, with 1-year, 2-year, and 3-year terms. Every year one CD matures, giving you cash flow, and you reinvest each maturity into a fresh 3-year CD. That way you keep annual liquidity while gradually locking more money into higher long-term rates. To compare the annualized effect of different rate scenarios, the CAGR calculator computes the true yearly growth rate for any plan.
One last reminder: deposit rates are not fixed — they move with the market. Before depositing, ask a few banks and line up the rates for CDs, regular deposits, and special products in a table. A few minutes of comparison can earn you hundreds more in interest every year.