Savings Interest Calculator
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.
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 the savings interest calculator when comparing options, setting a realistic target, or checking whether a proposed financial decision fits your broader plan.
Limitations
- The result is an estimate based on the amounts, rates, timing, and assumptions entered.
- Actual product terms, taxes, fees, eligibility rules, and market conditions can change the outcome.
- Use official disclosures or a qualified professional before making a binding financial decision.
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
- Using an advertised rate without checking whether it applies to the full balance or term.
- Leaving out fees, taxes, timing differences, or irregular cash flows.
- Treating a planning estimate as a guaranteed quote or final professional calculation.
Tips
- Run a conservative scenario as well as an optimistic one.
- Change one assumption at a time so you can see what drives the result.
- Save or export the calculation and update it when rates, costs, or goals change.
Sources and editorial review
Educational estimates only; not personalized financial, tax, legal, lending, investment, or insurance advice.