Savings Interest Calculator
Project how a savings balance can grow from your starting amount, monthly contributions, APY, and time horizon. The results separate the money you add from the interest the account earns.
You can also compare a second APY using the same balance and contribution schedule, or switch to a stated interest rate and choose its compounding frequency.
Your numbers
Example loaded: $10,000 starting savings, $300 added each month, 4.00% APY for 5 years, compared with 0.50% APY.
Use the APY shown by the savings account when you have it. APY already reflects compounding, so the calculator doesn't apply a separate compounding-frequency adjustment in APY mode.
Savings plan
Interest rate
How this calculator works
In APY mode, the calculator converts the annual percentage yield to an equivalent monthly rate. In stated-rate mode, it first converts the stated annual rate and selected compounding frequency to an equivalent APY, then uses the same monthly projection engine.
Each month applies interest before or after the contribution based on the timing you choose. The projection keeps fractional cents internally and rounds displayed dollar amounts to the nearest cent.
Results
Your projected savings growth
The projection holds the entered rate and monthly contribution constant for the full period. Actual account results can change when rates, balances, deposit dates, or withdrawals change.
APY comparison
Both scenarios use the same balance, contribution schedule, and time horizon.
Contribution vs. interest growth
Each bar separates money contributed from interest earned. When APY comparison is on, the dashed marker shows the comparison scenario's ending balance at the same point. Hover or tap a bar for details.
Yearly savings timeline
Each row shows the interest and contributions added during that period, plus the ending balance and cumulative interest.
| Period | Starting balance | Contributions | Interest | Ending balance | Cumulative interest |
|---|
APY and a stated interest rate are not the same input
APY is designed to show the effective annual yield after compounding. If an account advertises a 4.00% APY, you can use that figure directly without choosing daily or monthly compounding again.
A stated annual interest rate works differently because its effective annual yield depends on how often interest compounds. That is why the compounding selector appears only when you choose Stated interest rate.
APY
Best when the account already gives you an annual percentage yield. The effect of compounding is already built into the annual figure.
Stated rate
Needs a compounding frequency before it can be compared with APY. The calculator converts it to an effective annual yield first.
Monthly projection
Uses one equivalent monthly rate so contributions and interest can be tracked consistently from month to month.
Why contribution timing changes the result
A contribution made at the beginning of a month has one more month to earn interest than the same contribution made at the end. The difference is usually small over a short period, but it can compound across years of regular deposits.
If your actual deposits arrive throughout the month, either choice is still an approximation. End of month is a conservative default because the new contribution doesn't earn interest until the following month in this model.
The optional comparison changes only APY. That makes the ending-balance difference easier to interpret because the starting balance, contributions, contribution timing, and time horizon are identical in both scenarios.
Where savings growth fits with other goals
Interest can help a savings goal, but the monthly contribution usually does most of the early work. If the money is for unexpected expenses, compare the balance with an emergency-fund target. If it is for a known cost or date, a sinking fund can tell you how much needs to be set aside on schedule.
If those savings priorities are already where you want them, you can also compare the monthly contribution with an extra debt payment. The tradeoff is different: savings preserves cash and earns interest, while an extra debt payment reduces a balance that may be charging a higher rate.
Savings interest calculator FAQ
Does APY already include compounding?
Yes. APY is an effective annual yield that reflects compounding. In APY mode, the calculator converts the entered APY to an equivalent monthly rate and doesn't apply a second compounding-frequency adjustment.
What if I only know the stated interest rate?
Choose Stated interest rate, enter the annual rate, and select how often it compounds. The calculator converts those inputs to an equivalent APY before building the monthly savings projection.
Should I choose beginning or end of month for contributions?
Use beginning of month if the full contribution is normally available near the start of each month. Use end of month if you want a more conservative timing assumption or if the contribution is usually made later. The difference comes from how long each deposit earns interest.
Does the calculator round interest every month?
No. The projection keeps fractional cents internally and rounds displayed values to the nearest cent. Banks can use their own daily accrual, crediting, and rounding rules, so an actual statement may differ slightly.
Why might my bank's result be different?
Savings accounts can use daily balances, changing APYs, specific deposit dates, withdrawals, fees, minimum-balance rules, and different interest-crediting schedules. This calculator uses a consistent monthly-equivalent model so you can compare planning scenarios without pretending to reproduce every institution's statement calculation.
Does the calculator include taxes on savings interest?
No. Interest is shown before taxes, fees, or inflation. The calculator also doesn't determine whether any particular interest is taxable for your situation.
Explore more calculators
- Emergency Fund Calculator Set an emergency savings target and estimate the time or monthly contribution needed to reach it.
- Sinking Fund Calculator Plan monthly savings for a known future expense and see what it takes to reach the target.
- Paycheck Budget Calculator Assign recurring bills, spending, and savings to actual paychecks and see what remains after each check.
- Irregular Income Budget Calculator Analyze uneven take-home income, set a conservative planning baseline, and estimate a cash-flow buffer for weaker months.
Learn more about savings interest
These guides explain how savings interest is calculated and why APY is usually the better number for comparing deposit accounts.