Savings Interest Calculator: Interest Earned and Ending Balance
A savings interest calculator projects account growth from a starting balance, recurring deposits, rate, and time. It is useful for comparing saving behavior and rate scenarios, but real account rates and deposit timing may change.
Quick answer
Interest compounds on both the starting balance and previously credited interest. Regular deposits can have a larger effect than small rate differences, especially over shorter periods.
At a glance
- What it calculates
- Calculate projected savings interest and ending balance with recurring deposits and an assumed annual rate.
- Who it is for
- US savers using a standard savings or money market account rather than a promotional high-yield account.
- Coverage
- United States (federal rules; state and local rules vary)
- Data and assumptions
- Monthly compounding at the entered annual rate, deposits at month end, and no fees, tax or rate changes.
- Cost
- Free, no signup, calculations run in your browser
- Last reviewed
- 2026-07-09
Calculator
How to use this calculator
- Enter the current savings balance.
- Enter the monthly contribution.
- Add an assumed annual rate and time period.
- Review deposits, interest, and ending balance.
Explanation
What it is
A savings interest calculator projects account growth from a starting balance, recurring deposits, rate, and time. It is useful for comparing saving behavior and rate scenarios, but real account rates and deposit timing may change.
How it works
The calculator uses monthly compounding and assumes each recurring contribution is made at the end of the month.
When to use it
Use it when comparing standard savings or money market accounts, or checking the interest a balance should earn over a set period.
Limitations
- Rates on savings accounts are variable and change with market conditions.
- Fees, tiered rates and balance caps are not modelled.
- Results are pre-tax.
Key terms
- Interest rate
- The percentage paid on a balance over a stated period.
- Compounding
- Adding earned interest to principal so it can earn future interest.
- Contribution
- New money deposited during the projection.
- Future value
- The projected balance at the end of the period.
Formula
The calculator uses monthly compounding and assumes each recurring contribution is made at the end of the month.
Worked example
With $5,000 saved, $300 added monthly, and a 3.5% annual rate for 10 years, the ending balance includes $41,000 of deposits plus accumulated interest.
FAQ
How do I calculate interest on savings?
For a simple annual estimate, multiply the balance by the annual rate. Compound projections also account for timing and interest on prior interest.
What is the difference between APR and APY for savings?
APY reflects compounding over a year, while a stated annual rate may not. Use the institution’s APY when comparing deposit accounts.
Does this include tax on interest?
No. The result is before any income tax that may apply.
What happens if the rate changes?
The projection assumes one rate. Recalculate with lower and higher scenarios for a variable-rate account.
When are monthly deposits assumed?
At the end of each month, which is slightly more conservative than beginning-of-month deposits.
Common mistakes
- Comparing a nominal rate with an APY.
- Assuming a variable savings rate holds for the entire period.
- Ignoring monthly maintenance fees that cancel out the interest.
- Forgetting that interest is taxable in the year it is credited.
Tips
- Compare accounts on APY so compounding is already included.
- Check the compounding frequency; daily and monthly compounding differ slightly.
- Keep an eye on introductory rates that revert after a few months.
- Set aside the tax due on interest, which is reported on Form 1099-INT.
Sources and editorial review
Educational estimates only; not personalized financial, tax, legal, lending, investment, or insurance advice.