High Yield Savings Calculator

Compare a high yield savings account with your current account over time.

How it is calculated

Each account is projected separately with the same deposits. The tool first converts the APY into an equivalent monthly rate, r = (1 + APY ÷ 100)1/12 − 1, so that twelve months of compounding give exactly the stated yearly yield. With n = years × 12, the balance is start × (1 + r)n + deposit × ((1 + r)n − 1) ÷ r, with each deposit made at the end of its month. Interest earned is the high-yield balance minus start + deposit × n, and the extra earned is the difference between the two balances. Rates are assumed constant, and tax and fees are ignored; in reality high-yield rates can change at any time. Years must be above zero.

Worked example

You hold 10,000 and add 300 a month for 5 years. A high-yield account at 4.5% APY is compared with a regular account at 0.4% APY. Total deposited: 10,000 + 300 × 60 = 28,000. High-yield balance: $32,559.35, so interest earned is 32,559.35 − 28,000 = $4,559.35. The regular account ends at $28,379.42. The extra earned by moving is 32,559.35 − 28,379.42 = $4,179.92, almost all of the high-yield interest.

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Common mistakes

  • Entering the monthly deposit as a yearly amount, or the reverse. The field is per month, so 3,600 a year must be entered as 300.
  • Putting the high-yield rate in both rate fields and expecting a comparison. The second field must be what your current account really pays.
  • Assuming today's rate lasts for five years. High-yield rates can change, so test a lower rate to see how the result moves.
  • Entering an interest rate rather than the APY. The tool already handles the compounding, so an APY figure from a bank is the right input.
  • Ignoring taxes on the interest. The balances shown are before tax, so your net gain from switching is smaller.

About this calculator

A high-yield savings account (HYSA) pays an annual percentage yield (APY) substantially above the U.S. national average savings rate — often several times higher, since online banks with lower overhead can pass the savings on as interest, while brick-and-mortar banks frequently leave standard savings accounts at a small fraction of a percent. Growth compounds over time, and with monthly deposits added on top, the difference between a high-yield and a regular account widens every month rather than staying fixed.

Personal finance advisors routinely point to this comparison as one of the easiest, lowest-risk ways to improve returns on cash, since a HYSA carries the same FDIC insurance as a standard account but can pay meaningfully more — moving an emergency fund or short-term savings goal from a near-zero-interest account to a high-yield one costs nothing and requires no change in risk tolerance, only where the money sits. Seeing the compounding gap in dollar terms, rather than just as a percentage-point difference in APY, is usually what convinces someone to actually make the switch.

Enter your starting balance, monthly deposit, high-yield APY and your current account’s rate, and this calculator projects both balances forward and shows you exactly how much more the high-yield account earns.

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