Savings Interest Calculator
Calculate how much your savings will grow with compound interest and regular deposits. See future value and total interest earned.
About this calculator
This calculator projects savings growth using the standard compound-interest formula for a lump sum plus regular deposits: the Initial Deposit compounds at the given rate for the full term, and each Monthly Deposit compounds for whatever time remains between when it lands and when the term ends, so early deposits earn more total interest than deposits made near the end. Monthly Deposit is always applied once per calendar month -- Compounding Frequency does not change how often you deposit, only how often the account itself compounds interest, so the two are independent settings. Compounding Frequency sets how often the stated Annual Interest Rate is actually applied -- more frequent compounding produces a higher effective yield from the same stated rate, which is exactly why Effective Annual Rate (the true annualized growth rate implied by the stated rate and Compounding Frequency alone) is reported separately from the Annual Interest Rate you entered; Effective Annual Rate depends only on those two inputs, not on Initial Deposit, Years, or Monthly Deposit.
Years has the largest effect on Future Value of any input here, because it determines how many compounding periods every dollar -- both the initial deposit and every monthly contribution -- gets to grow through; doubling the number of years does not just double the interest earned, it compounds it. This calculator assumes a fixed rate for the entire term and deposits made on a strict monthly schedule with no withdrawals, gaps, or rate changes -- real savings and money market rates commonly move with the broader interest-rate environment, and this tool does not model that variability.
Financial Disclaimer
This calculator is for educational purposes only and does not constitute financial advice. Results are estimates based on the inputs provided. Consult a qualified financial advisor before making investment or financial planning decisions.
Inputs
Results
Future Value
$16,686.80
≈ 8 gaming PCs
Total Interest Earned
$3,686.80
≈ 4 smartphones
How to Use This Calculator
- Enter your initial deposit or current savings balance.
- Set the annual interest rate for your savings or money market account.
- Enter the number of years you plan to save.
- Add a monthly deposit if you plan to make regular contributions -- it's always applied once a month, independent of the compounding frequency you choose.
- Choose the compounding frequency — most savings accounts compound daily or monthly.
- Review the future value, total deposits made, and total interest earned.
How the result changes with Years
| Years | Future Value | Total Interest Earned |
|---|---|---|
| 5 | $7,966.35 | $966.35 |
| 7.5 | $12,082.03 | $2,082.03 |
| 15 | $27,603.02 | $8,603.02 |
| 25 | $58,373.54 | $27,373.54 |
What each input means
- Initial Deposit
- Starting amount
- Annual Interest Rate
- Nominal annual interest rate (APR) before compounding -- Effective Annual Rate below is the true APY once Compounding Frequency is applied.
- Years
- Number of years to save
- Monthly Deposit
- Additional monthly deposits (optional). Applied once per calendar month regardless of Compounding Frequency.
- Compounding Frequency
- How often interest is compounded. Monthly Deposit is unaffected by this choice.
How this is calculated
Formula
FV = P × g^(12t) + PMT × [(g^(12t) − 1) / (g − 1)], where g = (1 + r/n)^(n/12) is the effective one-month growth factor for a nominal rate r compounded n times/year (PMT deposits monthly regardless of n)Worked example, using the default values
- Identify Input Parameters5 parametersInitial Deposit = 1000, Annual Interest Rate = 4.5, Years = 10, Monthly Deposit = 100 = 5 input(s) provided
- Calculate Future ValueFuture Value16686.8 = $16,686.8
- Calculate Total Interest EarnedTotal Interest Earned3686.8 = $3,686.8
- Calculate Total DepositsTotal Deposits13000 = $13,000
- Calculate Effective Annual RateEffective Annual Rate4.59 = 4.59%
Engine last updated . Checked against 3 independently-derived tests — how we verify calculators. Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.
Frequently Asked Questions
What does Compounding Frequency actually change?
It changes how many times per year the stated Annual Interest Rate is applied to the balance. More frequent compounding -- daily versus monthly, for example -- applies smaller amounts of interest more often, which produces a slightly higher Future Value and a slightly higher Effective Annual Rate from the same stated rate, even though the difference is usually modest at typical savings rates.
Why is Effective Annual Rate different from the Annual Interest Rate I entered?
Annual Interest Rate is the stated nominal rate before compounding is applied; Effective Annual Rate is the true annualized growth rate implied by that stated rate once Compounding Frequency is applied -- the standard APY calculation, (1 + rate/n)^n − 1. It depends only on Annual Interest Rate and Compounding Frequency, not on Initial Deposit, Years, or Monthly Deposit, so adding or removing a monthly contribution never changes it. The two rates match only when compounding happens once a year; otherwise Effective Annual Rate is always slightly higher, because interest itself starts earning interest within the year.
Does increasing Years always help by roughly the same amount each time?
No -- because interest compounds, adding another year to a longer savings horizon adds more Total Interest Earned than adding a year to a short one, since a larger accumulated balance is compounding by the time that extra year arrives. This is why Years has the largest effect on Future Value of any input in this calculator.
What happens if I set Monthly Deposit to zero?
The calculator still compounds the Initial Deposit at the given rate and Compounding Frequency for the full term, but Total Deposits and Future Value will only reflect growth on that lump sum -- there is no ongoing contribution adding to the balance, so long-term growth depends entirely on the Initial Deposit and the rate.
Does a higher Annual Interest Rate always translate directly to a proportionally higher Future Value?
Not proportionally -- because interest compounds over Years, a higher rate increases Future Value more than a simple linear scaling would suggest, especially over longer terms. Two accounts with rates that differ by the same number of percentage points can end up with very different Future Values depending on how many years and deposits are involved.
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