How to calculate savings
PMT = (Goal − S(1+r)ⁿ) × r ÷ ((1+r)ⁿ − 1)
Worked example. Save each month: $465 / month.
Example inputs — Savings goal: $20,000; Already saved: $2,000; Years to reach goal: 3 yrs; Interest rate (APY): 4%. Starting values are illustrative.
From George Guju, founder of Calculyn · Educational calculator guidance, not professional advice.
How it works
We grow what you've already saved at your interest rate, then work out the level monthly deposit that closes the gap by your deadline.
Using the savings estimate
A savings target becomes more actionable when it is translated into a recurring deposit. This year-based goal calculator starts with what you already have, grows it under a constant rate and finds the monthly contribution needed to reach the target. Use it for a purchase, reserve or other planned expense with a known horizon. The deposit amount is a mathematical scenario, not evidence that the interest rate will remain available throughout that period.
Step-by-step inputs
- Savings goal. Use the amount needed at the end of the horizon. If your goal is priced in today's dollars, consider whether its cost could change before then. Starting example: $20,000 .
- Already saved. Enter only money already set aside for this goal. Savings needed for another purpose should not be counted again. Starting example: $2,000 .
- Years to reach goal. Enter the time available in years. The engine turns that horizon into monthly deposit periods. Starting example: 3 yrs.
- Interest rate (APY). Despite the APY field label, this engine uses the annual percentage divided by 12 as its monthly rate. An institution's effective APY may therefore produce a slightly different estimate. Starting example: 4% .
Worked example with the starting values
Using the starting inputs, the estimate is Save each month: $465 / month.
Existing savings first grow across the whole horizon. The remaining target gap is funded by repeated monthly deposits, each with less time to grow than the starting balance. Total deposits in the breakdown are new contributions, not the starting money; the remaining growth is the modeled interest.
- Total you'll deposit
- $16,754
- Interest earned
- $1,246
Compare years to reach goal scenarios
All other inputs stay at their starting values. These are modeled comparisons, not quotes, predictions or individual recommendations.
| Years to reach goal | Save each month |
|---|---|
| 2 yrs | $716 / month |
| 3 yrs | $465 / month |
| 5 yrs | $265 / month |
Make a useful comparison
Test a zero-rate case before relying on interest. It shows how much of the target must be supplied directly by saving when returns contribute nothing. If that monthly amount is unaffordable, consider a longer timeline, a smaller goal or more starting funds.
Compare horizons with the same goal and rate. A longer saving period spreads the target across more deposits and adds modeled growth time. It can also give prices more time to change, so revisit a purchase goal using realistic future costs.
Choose a savings vehicle consistent with when the money is needed. A smooth fixed-rate projection does not make a volatile investment suitable for a short deadline. Access restrictions and account terms belong in the practical plan even when they are not in the formula.
Common mistakes to avoid
- The starting balance is not a future contribution. Counting it in both current savings and planned deposits overstates what you are putting aside.
- Taxes, fees and variable rates are not deducted. Compare the estimate with actual account terms, including how the quoted yield is defined.
- A fixed end target and regular monthly deposits do not guarantee that irregular bills fit your cash flow. Schedule contributions around your income and keep a buffer for required expenses.
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Assumptions & limitations
- A constant rate of return or inflation every year.
- Excludes fees and taxes unless entered.
- Contributions are made regularly and on time.
Formula and assumptions reviewed October 2026 by the Calculyn team. How we build our calculators
Frequently asked questions
How long does it take to save $10,000?
Without interest or starting savings, $250 monthly takes 40 months. With an existing balance or interest it changes. This tool solves the monthly deposit for a selected deadline; enter $10,000 as the goal and compare timelines.
How much should I save each month for a goal?
Subtract the projected growth of your existing savings from the goal, then calculate the regular monthly deposits needed by your deadline. At zero interest this is simply the remaining gap divided by months.
Does a savings calculator include interest?
This one does. It converts the entered APY into an effective monthly rate and assumes end-of-month deposits with steady growth. Set APY to zero for a no-interest plan; taxes and account fees are not included.
What if I already have a starting balance?
Enter it under Already saved. The tool grows that balance through the selected years before calculating the remaining deposit need. Do not include the same starting cash again as a future deposit.
What is a good monthly savings amount?
Use the amount your after-tax budget can sustain while covering essential bills and debt obligations. The calculated deposit is what this goal needs, not a personal recommendation; extend the deadline or revise the goal if it is unaffordable.
How does compound interest grow my savings?
Interest added to savings earns further interest. Earlier deposits have more time to grow than later ones. The savings goal estimate includes growth of the initial balance and each modeled end-of-month deposit.
How big should an emergency fund be?
A common guideline is 3–6 months of essential expenses.
Are the deposits made all at once?
No. The estimate uses regular monthly deposits, so later deposits have less growth time than the starting balance.