The formula
How to calculate savings goal
This answers the question a savings target actually raises: given what is already in the account and what you can add each month, when does it get there? Interest earned along the way pulls the date forward.
The formula solves the future-value equation for time rather than amount, which is why a logarithm appears. Everything is handled monthly, so an annual return of 4% is applied as roughly 0.327% a month.
Fill in the following:
- Savings goal
- Saved so far
- Adding each month
- Annual return (%)
Results appear immediately — there is nothing to submit. Changing a field rewrites the link, so you can share the exact scenario you are looking at.
Worked example
Take the figures the calculator starts with:
- Savings goal: 25,000
- Saved so far: 5,000
- Adding each month: 500
- Annual return: 4 %
That gives:
- Months to reach it: 36.47 months
- Years to reach it: 3.04 years
- Of which your own deposits: 18,234.45
Reading the result
Compare the deposits line against the goal. The difference is what growth contributed — on short goals that is a rounding error and the return assumption barely matters, while on goals beyond about seven years it starts to carry real weight.
Where this goes wrong. Using an optimistic return on a short goal. Money needed within five years generally belongs in cash, where the honest rate is whatever the savings market pays, not an equity return you may not have when the date arrives.
For a cash goal, use the rate your account actually pays. For anything ten years or further out held in a diversified equity fund, 4–5% after inflation is a defensible planning figure, and being wrong on the low side is the cheaper mistake.
Early on, the monthly amount dominates — deposits are almost the whole balance. The longer the horizon, the more starting date matters, because it is the years of compounding you cannot buy back later.
The headline figure is months to reach it. With 25,000 savings goal, 5,000 saved so far and 500 adding each month, that comes to 36.47 months. Change any field and the figure moves with it.