Savings Goal Calculator

The same maths, asked backwards

The compound interest calculator starts from a contribution and asks what balance it grows into. This tool starts from the balance you want and asks the two questions that actually come up when you are planning toward something: how much do I need to save each month, and how long will my current saving take? Both answers come from running the same simulation backwards rather than a different formula, so if you already trust one calculator you can trust this one.

The rate is the input people get wrong

The single most common mistake with a tool like this is entering an ambitious rate of return for a goal that is only a few years away. A three-year house deposit does not belong in equities. The stock market's long-run average is real, but it is an average across decades that include multi-year stretches of losses, and a savings goal on a fixed date cannot simply wait out a downturn that happens to land right before you need the money. For a goal inside about five years, use the rate on an account you could actually hold the money in the whole time — a high-yield savings account, a CD that matures on schedule, or short-term Treasury bills. Save a stock-market assumption for goals genuinely a decade or more away, where a bad few years has time to be followed by a recovery.

Sizing an emergency fund

If the goal is an emergency fund rather than a purchase, the target itself follows a rule of thumb: three to six months of essential expenses. Essential means what keeps the household running — housing, utilities, food, insurance, minimum debt payments — not your full current spending, which usually includes discretionary items you would cut in an actual emergency. Push toward six months or more with a single income, variable or commission pay, or a specialised job that would take a while to replace. Three months is more defensible with two stable incomes and low fixed costs. Whatever the target, keep it in cash or a high-yield savings account: the entire point of this money is that it is there, undiminished, exactly when something goes wrong, which rules out anything that can lose value on a bad day.

Inflation and which dollars you mean

For anything more than a few years out, a dollar target quietly loses meaning unless you decide what it is a dollar of. Two consistent conventions both work: enter the target in today's purchasing power and use a real rate of return (your expected return minus expected inflation), or enter the actual number you want the account to show on the date and use a nominal rate. Mixing them — a today's-dollars target with a nominal rate — understates what you will actually need, because it quietly assumes the target itself does not inflate while your money does.

When the required contribution is not affordable

Run the numbers and the required monthly contribution can come out higher than the budget allows. There are exactly three levers, and every fix is one of them:

• Extend the horizon. More months means more time contributing and more time compounding, so the required monthly amount drops. This is usually the cheapest fix and costs you only patience.
• Lower the target. The most direct lever, and the right one when the original number was a round figure rather than something you actually costed out.
• Accept a higher expected return. This lowers the contribution the calculator asks for, but it does so by adding risk: an equity return that disappoints in the years right before your date leaves you short, which is exactly the failure mode the rate advice above is warning against.

There is no fourth lever. Any plan that looks easier than these three is quietly choosing one of them without saying so.