The Savings Goal Calculator answers the savings question in both directions. In required-contribution mode, give it a target, a deadline, your current savings, and an interest rate, and it solves for the exact monthly contribution. In time-to-goal mode, give it the contribution you can actually make, and it returns the month you arrive — with the dates you cross 25%, 50%, and 75% of the goal along the way.
How It Works
Current savings are first grown to the deadline on their own; only the shortfall needs funding:
The time-to-goal mode inverts the same annuity math with logarithms and rounds up to whole months, so the final amount lands at or just past the target rather than a fraction short. Compounding and contribution frequencies can be changed from the monthly defaults if your account compounds differently.
Worked Example 1: Required Contribution
Target 10,000, rate 4.5%:
- Future value of current savings: 12,517.96**
- Shortfall to fund: 12,517.96 = $37,482.04
- Required monthly contribution: $558.22
- Over 60 months you contribute 6,506.75 — about 13% of the house deposit is paid by compounding rather than by you.
Worked Example 2: Time to Goal
Target 2,000, contributing 20,478.07 (the overshoot is the rounding-up of the final month), with 1,978.07** of interest. Milestones on the way: 25% (10,000) in month 26, 75% ($15,000) in month 41. Halfway in dollars takes 26 of 55 months — but the last quarter arrives in 14 months, because the balance compounding underneath keeps growing. That back-loaded shape is why the middle of a savings plan feels slowest.
Using the Two Modes Together
The honest workflow: run required-contribution mode first to see the price of your deadline. If 400 a month, say — and negotiate with the date instead of abandoning the target. The three levers are always the same (target, time, contribution), and the calculator's job is to make the trade between them explicit before life makes it for you. A rate change is the fourth lever but the weakest one to rely on: chasing yield on money earmarked for a near-term goal trades certainty for return on the funds that can least afford the risk.
Limitations
The rate is held constant and gross of tax; high-yield savings rates move with central-bank policy, and interest is taxable income in most jurisdictions. Results assume contributions land every period without fail and the target stays fixed — goals with inflation exposure (a house deposit in a rising market is the classic case) should have their target revisited annually, not just their contribution. If your current savings alone already grow past the target, the required contribution is returned as zero rather than an error; in time-to-goal mode, a goal already reached is reported as such.
Frequently Asked Questions
What interest rate should I enter?
The rate on the account the money will actually sit in: a high-yield savings account's current APY for cash goals, or a conservative expected return for invested goals with long horizons. Re-run the plan when the rate changes materially — the required contribution in Example 1 moves by roughly $23 a month for every point of rate.
Why does the final amount in time-to-goal mode overshoot the target?
Because contributions are monthly and indivisible in the model: the goal is crossed partway through the final month, but the whole month's contribution and interest are counted. The overshoot ($478.07 in the example) is a small free head start on the next goal, not an error.
Should my emergency fund use this calculator too?
Yes — it is the same problem with a target defined by expenses rather than a purchase: three to six months of essential spending as the target, current savings as the starting point, and your actual spare cash flow as the contribution in time-to-goal mode to see when you are covered.