Savings Growth Calculator
Calculate savings growth with regular contributions
Reliable calculator with instant results. Clean interface, accurate computations.
Formula
FV = P(1+r)^n + PMT[((1+r)^n - 1)/r]How to Use Savings Growth Calculator
- Fill in the calculator with your numbers.
- Verify your inputs are correct.
- Read the instant calculation results.
- Copy or apply the results as needed.
Examples
This calculates how a savings balance grows when you combine a starting deposit with regular monthly contributions that themselves earn interest, which is the shape of most goal-based savings, an emergency fund, a house deposit, or a sinking fund for a big purchase. The contributions matter more than the starting balance for most people, because a small regular deposit compounding for years usually outgrows a larger one-off deposit left untouched for the same period.
The formula
FV = P(1+r)^n + PMT x [((1+r)^n - 1) / r]- FV
- the future value of the account
- P
- the starting balance
- PMT
- the fixed amount deposited each period
- r
- the periodic interest rate (annual rate / 12 for monthly)
- n
- the total number of periods
Worked example
Start with $1,000, add $200 every month, at 4% a year compounded monthly, for 10 years. The monthly rate is 0.0033333 and n = 120, giving (1.0033333)^120 = 1.490832. The starting balance grows to 1000 x 1.490832 = $1,490.83, and the deposits grow to 200 x [(1.490832 - 1) / 0.0033333] = $29,449.94. The account totals $30,940.78 against $25,000 actually deposited, a gain of $5,940.78 from interest.
What trips people up
- Whether deposits land at the start or end of each month changes the answer slightly, because a deposit at the start earns one extra period of interest.
- A quoted savings rate is usually annual. Forgetting to convert it to a monthly rate before applying it to monthly deposits overstates the total.
- Interest earned inside most savings accounts is taxable in the year it is credited, even if you never withdraw it.
- Stopping contributions early costs more than the missed deposits alone, because those deposits also lose all the compounding time they would have had.
Frequently asked questions
- Does it matter whether I deposit at the start or end of the month?
- Slightly. A deposit at the start of the period earns interest for that whole period; the same deposit at the end earns nothing until the next period, so start-of-period deposits produce a marginally higher final balance.
- How much of my final balance comes from interest versus my own deposits?
- Add up your starting balance plus every contribution to get total deposited, then subtract that from the future value; the remainder is interest, and its share grows the longer the money sits.
- Is a higher starting balance or a higher monthly contribution better for growth?
- Over a long horizon, consistent monthly contributions usually contribute more to the final total than a larger starting lump sum, simply because more of the contributed money has been sitting in the account for longer, on average.
- What happens if the interest rate changes partway through the term?
- The formula assumes one constant rate for the whole period. A rate change means splitting the calculation into two segments, using the balance at the change date as the starting point for the second segment.
- Is interest on a savings account taxed the same way every year?
- In most tax systems, interest is taxed in the year it is credited to the account, whether or not you withdraw it, so the tax bill and the compounding both happen annually even inside a multi-year savings plan.