Savings Growth Calculator
Use our free savings growth calculator to see how your money grows — weekly, monthly, or yearly contributions, promotional rates included.
Calculate Your Savings Growth
Enter the promotional rate your bank is advertising, how long it lasts, and the standard rate it reverts to — this shows what you’ll actually earn, not what the homepage implies.
Works as a weekly savings calculator, a monthly one, or a yearly one — pick whichever matches how you actually contribute from the dropdown below.
| Phase | Duration | Rate | Balance at end of phase |
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How to Use This Calculator
Here’s how to get an accurate answer out of this savings account interest calculator in under a minute, whether you’re contributing weekly, monthly, or yearly.
Whatever’s already sitting in the account today. Enter 0 if you’re starting from scratch.
Enter how much you plan to set aside, then pick weekly, monthly, or yearly from the dropdown next to it. This also works as a standalone weekly savings calculator or a monthly saving growth calculator — we convert whichever frequency you choose into a monthly-equivalent behind the scenes.
If the account has a promotional rate, leave “Has a promo rate” selected and fill in the teaser APY plus how many months it lasts. If it’s a flat-rate account with no introductory offer, switch to “Flat rate only” and enter just the one rate.
How many years you plan to keep contributing and let the balance grow before you need the money.
Results update instantly as you type, no button required. You’ll see what you’ll actually get, what the headline rate implies if it applied the whole time, what you’d have with no promo at all, and the effective blended APY as a single percentage — plus a phase-by-phase breakdown below.
Understanding Savings Growth (and Why the Headline Rate Isn’t the Whole Story)
What Is a Savings Growth Calculator?
A savings growth calculator projects how a deposit plus regular contributions grows over time at a given interest rate, using compound interest. Nearly every version of this tool online assumes one flat rate for the entire period — which is a reasonable simplification for a plain savings account, but not for a high-yield account advertising a promotional rate.
What Is a Teaser or Promotional Rate?
Many high-yield savings accounts advertise an elevated APY to attract new deposits, guaranteed only for an introductory window — often three to six months. After that window closes, the balance automatically reverts to the account’s standard, usually meaningfully lower, ongoing rate. This is a well-documented pattern across the industry, not a rare edge case, and it’s worth reading the fine print on any “top rate” account before opening one.
Why the Real Number Is Usually Lower Than It Looks
If a bank advertises “5.00% APY” and you calculate your growth using that rate for the full time you plan to keep the money, you’re calculating a number the bank never actually promised you. The real, blended return — the elevated rate for a few months, then the lower standard rate for the rest of the time — is almost always meaningfully lower than the headline number implies, especially over a multi-year horizon where the promotional window is a small fraction of the total time.
Key Terms, Explained
How This Is Calculated
The calculator runs two phases of compound interest back to back instead of one flat calculation. Each month, interest is added to the current balance at that month’s applicable rate, and then that month’s contribution is added on top:
Months 1 through promo length use the teaser rate ÷ 12
Remaining months use the standard rate ÷ 12
This is the same core savings plan formula calculator logic used by most compound-growth tools — we just run it twice, once per rate phase. If you entered a weekly or yearly contribution, it’s converted to a monthly-equivalent first: weekly amounts are multiplied by 52 and divided by 12, yearly amounts are divided by 12, so everything runs through the same monthly loop above.
The “What the Headline Rate Implies” figure runs the entire time horizon at the teaser rate alone — the number you’d get if you (incorrectly) assumed the advertised APY applied the whole time. The “If You Never Got the Promo” figure runs the entire horizon at the standard rate alone, as a baseline for what you’d have earned without the promotional bump at all. We also surface the effective blended rate as a single percentage, so this doubles as a savings percentage calculator rather than just a dollar total.
This is an educational modeling tool, not a quote from any specific bank. Actual account terms, compounding schedules, and rate changes vary by institution and are not guaranteed to match the inputs you enter here.
Investing & Savings Tools
This calculator handles the promotional-rate reality check. For the rest of the savings-and-investing picture, these tools use the same transparent, sourced-data approach.
Frequently Asked Questions
An elevated APY a bank offers for a limited introductory period — often three to six months — to attract new deposits. Once that window ends, the account automatically reverts to a lower standard rate, whether or not you notice the switch.
Check the account’s terms and conditions, specifically for language like “introductory,” “promotional,” or “for new customers only,” along with a stated expiration period. If the advertised rate has no such qualifier and no expiration date mentioned, it’s more likely a standard ongoing rate — but it’s still worth confirming directly with the bank, since rates can still change with notice.
It depends on the size of your balance and how much time switching takes versus the extra interest earned. For a large balance over a full promotional window, the extra interest can be meaningful. For a small balance, the effort of moving direct deposits, closing accounts, and tracking multiple institutions may not be worth a few extra dollars — run your own numbers through this calculator first.
Usually a small one. Daily compounding versus monthly compounding at the same stated APY typically differs by a fraction of a percentage point in effective yield over a year. It matters far less than whether you’re comparing the promotional rate to the standard rate correctly.
Regular savings calculators assume one flat rate for the entire period you enter. This one runs two rates back to back — a promotional rate for a set number of months, then a standard rate for the rest of the time — and shows you the realistic blended result next to what the flat-rate assumption would have implied.
Yes. Pick weekly from the contribution frequency dropdown (monthly and yearly are also options) and it runs the same compound-growth math on a steady weekly deposit instead of a monthly one. One thing worth flagging: this models a flat weekly amount, not the escalating $1-then-$2-then-$3 format used by 52-week savings challenges — if that’s specifically what you’re doing, the totals here won’t match, since this assumes the same amount every week.
Not quite. This tool projects forward from what you enter — starting balance, contributions, and rate — to a balance at the end. A savings goal calculator works backward from a target number to tell you how much to contribute. You can approximate that here by adjusting the contribution amount above until the projected balance matches your target.
This version models accumulation only — money going in, not coming out. A savings withdrawal calculator models the opposite: starting with a balance and drawing it down over time, which is a different calculation from the one this tool runs.
This is built around a fixed, bank-stated APY, which is what makes the promotional-to-standard-rate modeling possible. As a saving growth calculator for the S&P 500 or other market investments, it’s only a rough approximation at best: stock returns aren’t fixed or guaranteed the way a savings account’s APY is, and they vary significantly year to year. You can still enter an assumed average return to get a simplified projection, but treat it as illustrative only.