How the monthly amount is worked out
Without interest, the answer is simple division: what you still need, divided by the number of months. 20,000 − 2,000 = 18,000 over 36 months is 500.00 a month.
With interest, your existing savings grow on their own and each deposit earns interest for the months that remain, so you need to put in a little less. The calculator assumes interest is compounded monthly and that you deposit at the end of each month:
i = annual rate ÷ 12, n = number of months
Monthly deposit = (goal − already saved × (1 + i)n) × i ÷ ((1 + i)n − 1)
For a goal of 20,000 in 3 years with 2,000 already saved at 4% a year: i = 0.04 ÷ 12 ≈ 0.003333 and n = 36. The 2,000 grows to about 2,254.54, and the monthly deposit comes to 464.77. You pay in 16,731.54 in total, and interest supplies about 1,268.46.
Monthly savings needed for 10,000
Starting from zero, depositing at the end of each month:
| Time frame | 0% interest | 2% | 4% | 6% |
|---|---|---|---|---|
| 1 year | 833.33 | 825.72 | 818.17 | 810.66 |
| 2 years | 416.67 | 408.74 | 400.92 | 393.21 |
| 3 years | 277.78 | 269.76 | 261.91 | 254.22 |
| 5 years | 166.67 | 158.61 | 150.83 | 143.33 |
| 10 years | 83.33 | 75.35 | 67.91 | 61.02 |
The table shows two things. Over short periods, interest barely changes the monthly amount; the time frame matters far more. Over ten years, a 6% return cuts the required deposit by more than a quarter.
More examples
- Emergency fund. Six months of expenses of 1,000 each, saved over 12 months with no interest: 6,000 ÷ 12 = 500 a month.
- Car deposit. 10,000 in 2 years at 5%, starting from nothing: about 397.05 a month, of which interest provides 470.87 in total.
- House deposit. 50,000 in 5 years with 5,000 already saved at 4.5%: about 651.44 a month. Interest contributes roughly 5,913.85.
- Four-year goal. 30,000 in 4 years at 4% from zero needs about 577.37 a month.
Making the plan realistic
- Automate the deposit on payday so the money moves before it can be spent.
- Use a conservative rate. Savings rates change, and investment returns are not guaranteed. If the goal is less than about five years away, many people keep the money in cash savings rather than shares.
- Allow for inflation. A goal priced in today's money, such as a car, may cost more when you buy it. Raise the goal by a few percent per year if the date is far away.
- Taxes and fees on interest reduce the effective rate. Enter the rate after tax if you know it.
Common mistakes
- Mixing annual and monthly rates. Enter the yearly rate (APY or AER); the calculator divides by 12.
- Ignoring what you already have. Existing savings also earn interest, which lowers the monthly amount.
- Choosing a deadline that needs more than you can spare. If the result is too high, extend the time frame and recalculate rather than skipping months.
Saving at the start of the month instead
If you deposit on payday at the beginning of each month, every deposit earns one extra month of interest. The required amount is the end-of-month result divided by (1 + monthly rate). In the main example, 464.77 ÷ 1.003333 = 463.22: a small saving over three years, but it grows with higher rates and longer time frames.
How long will a fixed amount take?
You can also run the calculation the other way. Saving 300 a month towards 20,000, starting with 2,000 at 4% interest, the balance passes the goal after 54 months (four and a half years), ending at about 20,111. Without interest it would take (20,000 − 2,000) ÷ 300 = 60 months. Try different time frames in the calculator until the monthly amount matches what you can afford.
Several goals at once
When you save for more than one thing, such as an emergency fund, a holiday and a car, calculate each goal separately and add the monthly amounts. Separate accounts or labelled "pots" make progress visible and stop one goal from quietly using another's money.
Frequently asked questions
How much should I save each month to reach my goal?
Without interest, divide the amount you still need by the number of months. With interest, use the formula on this page; 20,000 in 3 years with 2,000 saved at 4% needs about 464.77 a month.
Does interest make a big difference?
Over one or two years, very little. Over ten years it matters: saving 10,000 needs 83.33 a month at 0% but about 61.02 a month at 6%.
Is the deposit made at the start or end of the month?
The calculator assumes the end of each month. Depositing at the start gives each payment one extra month of interest, so the required amount is slightly lower.
What interest rate should I use?
Use the rate your savings account currently pays, or a conservative estimate for investments. Rates change, so recalculate every few months.
How long does it take to save 20,000 at 300 a month?
Starting with 2,000 at 4% interest, about 54 months. Without interest, (20,000 − 2,000) ÷ 300 = 60 months.
Sources
- Consumer Financial Protection Bureau (US), guidance on setting savings goals and building an emergency fund.
- Standard future-value-of-an-annuity formula, as used in finance textbooks and spreadsheet functions such as PMT.
Last reviewed 6 October 2026. Results are estimates; see our disclaimer.