Savings Calculator: Future Balance, Interest and Monthly Income
This savings calculator projects what a savings account will hold after a number of years. Enter a starting balance, a monthly deposit and your account’s APY, and it shows the Future Balance, how much of it is your own money, how much is interest, and the Monthly Income (final year) that interest pays. There is no button to press: the numbers update as you type. It also works as a high yield savings calculator, because the default rate type is APY, the figure high yield accounts advertise. The sums run in your browser, and nothing you enter is uploaded or saved.
How to calculate your savings balance
- Enter your starting balance in Initial Deposit. Use 0 if you are starting from nothing.
- Enter what you add each month in Monthly Contribution. The hint under the label says it is added at the end of each month.
- Enter the rate in APY (%). If your bank quotes a plain rate instead, press Interest rate under the fields and the label becomes Annual Interest Rate (%).
- Enter Years to Grow, a whole number from 1 to 150.
- Read the result card at the top. Below it, the Growth over time chart shows one bar per year, split into principal and interest.
The fields open with an example so you can see the layout: in US dollars, 5,000 to start, 200 a month, 4.5% APY and 10 years. Amounts are shown in the currency of your region.
Total Principal: 29,000.00
Total Interest: 8,859.98
Monthly Income (final year): 131.16
Total Principal is the 5,000 plus 120 deposits of 200. The other 8,860 is interest the account added.
APY or interest rate: which one to enter
An interest rate is the yearly rate before compounding. APY is the yearly result after compounding, so it is the number to use when your account lists one, as most savings accounts do. The two buttons under the fields switch between them, and the same percentage gives different results:
| Rate type | Compounding | Future Balance after 10 years |
|---|---|---|
| APY, 4.5% | Already included | 37,859.98 |
| Interest rate, 4.5% | Annually | 37,859.98 |
| Interest rate, 4.5% | Monthly | 38,074.58 |
| Interest rate, 4.5% | Daily | 38,094.08 |
All four rows use 5,000 to start and 200 a month. A 4.5% interest rate compounded monthly is the same as an APY of about 4.59%.
Reading the result card
| Line | What it shows |
|---|---|
| Future Balance | The projected balance after the Years to Grow, labelled “after 10 years” and so on. |
| Total Principal | Initial Deposit plus every monthly contribution. Your own money. |
| Total Interest | Future Balance minus Total Principal. |
| Monthly Income (final year) | The interest earned in the last 12 months, divided by 12. It is the monthly payout your balance would be generating by then. |
| After-Tax Interest | Total Interest with your Tax Rate taken off. Shown only when Tax Rate is above 0. |
| Purchasing Power (today’s money) | Future Balance reduced by the Inflation Rate for each year. Shown only when Inflation Rate is above 0. |
Monthly interest income from your savings
Monthly Income (final year) answers the question “how much interest will this pay me each month?” It averages the last 12 months, so with regular deposits it is higher than the first year’s figure. To get the monthly interest on a balance you already have, set Monthly Contribution to 0 and Years to Grow to 1.
Monthly Income (final year): 375.00
Advanced: compounding, inflation and tax
Press Advanced: compounding, inflation & tax to open three more fields.
- Compound Frequency: Daily, Monthly or Annually, and Monthly is the default. It applies only when the rate type is Interest rate. With APY selected the field is disabled and a note says why, because an APY already includes compounding.
- Inflation Rate (%): adds the Purchasing Power (today’s money) line, which divides Future Balance by (1 + inflation) for each year.
- Tax Rate (%): adds the After-Tax Interest line, which takes your tax rate off Total Interest.
Purchasing Power (today’s money): 28,171.38
After-Tax Interest: 6,910.79
The tax line applies one flat rate to all the interest and is shown beside the other figures. The Future Balance and Monthly Income lines stay before tax.
Limits
| Field | Allowed |
|---|---|
| Initial Deposit, Monthly Contribution | 0 or more, decimals allowed |
| APY (%) or Annual Interest Rate (%) | 0 to 100. A rate of 0 works: the balance is just your deposits. |
| Years to Grow | Whole years, 1 to 150 |
| Inflation Rate (%), Tax Rate (%) | 0 to 100 |
A value outside these ranges is calculated as the nearest allowed one, and an empty field counts as 0 (10 years for Years to Grow), so the result never breaks. The chart shows at most 30 bars; a longer period is thinned so the last bar is always the final year.
How the balance is calculated
Deposits go in at the end of each month. With a rate that compounds monthly, the Future Balance is A = P(1 + r/12)12t + PMT((1 + r/12)12t − 1) / (r/12), where P is the Initial Deposit, PMT the Monthly Contribution, r the yearly rate as a decimal and t the years. When you enter an APY, the monthly rate is (1 + APY)1/12 − 1, so a year of growth ends exactly at the APY you gave.
Total Principal: 190,000.00
Total Interest: 501,150.47
What this calculator does not do
- It is a projection from the numbers you enter, not financial advice and not a guarantee of any rate or balance. Real savings rates change, and the calculator holds yours the same for every year.
- It has no withdrawals, no one-off deposits and no changing contribution. The deposit is the same every month.
- It does not include fees, and it does not model tax-free or tax-deferred accounts. Tax is one flat rate on the interest.
- Years to Grow is in whole years, up to 150.
Related jobs have their own tools: the compound interest calculator goes into daily and monthly compounding detail, the inflation calculator works out what prices will be, the real return calculator removes inflation from a rate, and the daily interest calculator shows how much interest accrues per day.
Frequently asked questions
How much interest will my savings earn?
Enter your balance in Initial Deposit, any regular amount in Monthly Contribution, your account's APY and the Years to Grow. Total Interest shows everything the account adds on top of what you paid in. With 5,000 to start, 200 a month and a 4.5% APY, the interest after 10 years is about 8,860 on 29,000 paid in. Banks change their rates, so treat the figure as an estimate.
What is the difference between APY and interest rate?
An interest rate is the yearly rate before compounding. APY (annual percentage yield) is what you actually end up with after one year of compounding, so it is the higher number when interest is added more than once a year. Pick the one your bank quotes. With APY selected, Compound Frequency is ignored because the APY already includes it. With Interest rate selected, the same 4.5% compounded monthly grows to about 38,075 over 10 years in the example above, against about 37,860 for a 4.5% APY.
How do I calculate monthly interest on a savings account?
For a quick figure, multiply the balance by the APY and divide by 12. For 100,000 at 4.5% that is 375 a month. The calculator does this for you and also handles deposits: the Monthly Income (final year) line is the average monthly interest earned in the last 12 months of your projection, so it reflects the balance you will have built by then.
How do I use a savings calculator with monthly deposits?
Type the amount you will add each month into Monthly Contribution. It is added at the end of each month, so the first deposit starts earning one month later. Leave Initial Deposit at 0 if you are starting from nothing. Total Principal then equals the deposits only, and Total Interest is the growth on top.
How much is $500 a month for 30 years?
Paying in 500 a month for 30 years means 180,000 of your own money. At a 4.5% APY it grows to about 373,500, of which about 193,500 is interest. At a 7% interest rate compounded monthly, an assumed investment-style return rather than a typical savings account rate, it grows to about 609,985. Set Initial Deposit to 0, Monthly Contribution to 500 and Years to Grow to 30 to see both. Amounts are shown in your regional currency.
How do I use this as a high yield savings calculator?
Keep the APY switch on, which is the default, and enter the APY your high yield savings account (HYSA) advertises. Add your balance and what you plan to deposit each month, then read Future Balance and Monthly Income (final year). The result assumes the rate stays the same for every year you enter, while real savings rates move up and down.
Can a savings calculator include inflation and tax?
Yes. Open Advanced: compounding, inflation & tax and fill in Inflation Rate (%) and Tax Rate (%). Purchasing Power (today's money) then shows the final balance in today's buying power, and After-Tax Interest shows Total Interest with your tax rate taken off. Each line appears only when its rate is above 0. With 3% inflation and a 22% tax rate, the 10-year example shows about 28,171 of purchasing power and about 6,911 of after-tax interest.
How much interest per month on $100,000 of savings?
At a 4.5% APY, 100,000 earns 4,500 over a year, which is 375 a month. To check any other balance, enter it in Initial Deposit, set Monthly Contribution to 0, set Years to Grow to 1 and read Monthly Income (final year). Over longer periods the monthly figure grows, because interest is earned on earlier interest.
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