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CALCPARK

Savings Goal Calculator

Find the monthly deposit needed to reach a savings target by a deadline, or how long a fixed monthly deposit takes, with interest and a progress bar.

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How to use it

  1. Choose the question: “How much per month?” when you have a deadline, or “How long will it take?” when you know what you can afford.
  2. Enter the target, what you have saved so far and the yearly interest rate of the account (leave it empty for cash).
  3. Enter the deadline in years and months, or the monthly deposit, depending on the mode.
  4. Read the monthly deposit or the time to goal, the total you will pay in, the interest earned and the progress bar.
  5. Copy the summary or the link to revisit the plan later.

Example

Target 20,000, nothing saved yet, 4% a year, deadline 5 years (60 months). The monthly rate is 0.04 ÷ 12 = 0.003333 and 1.003333⁶⁰ = 1.2210. Required deposit = 20,000 × 0.003333 ÷ (1.2210 − 1) = 301.66 a month. Total deposits 18,099.83, interest 1,900.17. In the other mode, 300 a month gives ln((20,000 × 0.003333 + 300) ÷ 300) ÷ ln(1.003333) = 60.3, so the goal is reached in 61 months, with a closing balance of 20,255.99.

Formulas and assumptions

i = yearly rate ÷ 12 ÷ 100,  N = months,  P = already saved,  G = target
Balance after N months:  B = P · (1 + i)^N + D · ((1 + i)^N − 1) / i
Monthly deposit:         D = (G − P · (1 + i)^N) · i / ((1 + i)^N − 1)        (i = 0:  D = (G − P) / N)
Months to goal:          N = ln((G · i + D) / (P · i + D)) / ln(1 + i)        (i = 0:  N = (G − P) / D), rounded up

These are the standard future-value-of-an-annuity formulas with deposits at the end of each month and interest credited monthly at the nominal rate ÷ 12. Assumptions: a fixed rate, a constant deposit, no fees, taxes or withdrawals. The time-to-goal answer is a whole number of months, so the final balance can slightly exceed the target. If the money you already have covers the goal at the deadline, the required deposit is shown as 0.

Sources: US SEC – Savings goal calculator, Consumer Financial Protection Bureau – How to save.

Projections only, not financial advice. Rates on real accounts change, and interest may be taxed.

Questions

Why does the time-to-goal result not divide evenly?
Deposits are whole months, so the calculator rounds up to the first month in which the balance reaches the target. At 0% interest, 1,000 saved at 99 a month takes 11 months, not 10.1.
Does inflation change the answer?
The formulas work in nominal money. If your target is in today’s prices and the deadline is far away, raise the target by expected inflation or enter the real interest rate (rate minus inflation) instead.
Can I use it for a yearly deposit?
Enter one twelfth of the yearly amount as the monthly deposit. The result is close but not identical, because the calculator credits interest monthly.