How does the savings growth calculator work?

The calculator uses the compound interest formula with regular monthly contributions. You enter a starting balance, a monthly saving amount, an APY and a time horizon. The tool then projects your future balance, total contributions and interest earned.

What APY should I use?

As a starting point, use the APY advertised by your savings account, CD, money market fund or investment product. You can also test more conservative or optimistic APYs to see how sensitive your savings plan is to changes in interest rates.

Are taxes and inflation included?

No. The calculator shows nominal balances before tax and inflation. To account for them, you can try a lower APY to approximate the real, after-inflation growth rate of your savings.

Can I use the calculator without monthly contributions?

Yes. Set the monthly contribution to zero and the calculator will show how a single lump sum grows at your chosen APY over the selected time period.

Savings Growth Calculator — See How Fast Your Money Can Grow

Projected future savings

—

Total contributions

—

Starting balance plus all monthly deposits.

Interest earned

—

Growth generated by APY and compounding.

Interest share

—

Portion of the final balance coming from interest.

Time horizon

—

Saving period in years and months.

Savings summary

Enter your savings plan above to see how much you could have in the future and how much of that total comes from interest.

Starting balance: —
Monthly contribution: —
Final balance breakdown: —

Contributions vs interest

Contributions — 100%
Interest — 0%

Balance over time (with monthly saving)

Projected savings balance

How this savings growth calculator works

Many savings tools focus only on a single lump-sum deposit. In real life, most people build savings with a mix of an initial amount and regular contributions from their paycheque. This calculator models both pieces together.

It treats the APY you enter as an effective annual rate that already includes compounding. From that APY, the calculator derives an equivalent monthly growth rate and applies it to each month in your saving period.

The basic idea is:

APY  = effective annual yield (decimal)
rₘ   = (1 + APY)^(1/12) − 1  (monthly rate)
N    = number of months

Balance₀ = starting balance
Balanceₙ = (Balanceₙ₋₁ × (1 + rₘ)) + monthly contribution

Repeating this step N times produces the final balance. The calculator also tracks how much you contributed along the way so it can show how much of your ending balance is your own deposits versus interest earned.

Example: saving for a house deposit

Imagine the following savings plan:

Starting balance: $2,500.
Monthly contribution: $400.
APY: 4.5% (0.045 as a decimal).
Saving period: 8 years.

Enter those numbers into the calculator. The tool will show a final balance in the region of tens of thousands of dollars, along with a breakdown of:

How much you personally contributed over the 8 years.
How much extra came from interest and compounding.
The percentage of your final balance that is “free growth”.

You can experiment with slightly higher APYs, longer saving periods or bigger monthly contributions to see how quickly your target becomes realistic.

Why APY is more useful than nominal interest rate

Banks sometimes quote a nominal rate such as “4% compounded monthly”. That rate does not yet include the benefit of compounding during the year. APY (annual percentage yield) goes one step further and tells you the actual yearly growth of your money after all the compounding effects are taken into account.

Using APY in a savings growth calculator makes it easier to compare different accounts — one might compound daily and another monthly, but their APYs can be compared directly.

Tips for planning your savings with this calculator

Start with the APY from your current savings account, then try 1–2% lower for a conservative scenario and 1–2% higher for an optimistic scenario.
Increase the monthly contribution in small steps to see how much faster you can hit a specific goal such as a deposit, tuition or emergency fund.
Remember that interest rates can change over time. Revisit your assumptions if your bank adjusts its APY.
For investments with higher risk (like stock index funds), you may want to test a wider range of possible APYs to understand best-, base- and worst-case outcomes.

Frequently asked questions

Can I set the monthly contribution to zero?

Yes. If you simply want a lump-sum compound interest calculator, set the monthly contribution to 0. The calculator will then show how your starting balance grows at the chosen APY.

Why doesn’t the calculator include taxes or inflation?

Tax rules and inflation rates vary by country and over time, so they are not built into the maths. To approximate their effect, many people choose a smaller APY that reflects their expected after-tax, after-inflation return.

Is my result guaranteed?

No. APY on savings accounts can move up or down, and market-based investments fluctuate in value. The calculator is a planning tool that shows what would happen if the APY remained constant over your chosen time period.