Savings goal calculator
Set a target and this calculator works backwards to your plan. In monthly mode it tells you how much to set aside each month to hit the goal in a fixed time; in time mode it tells you how long a chosen monthly amount will take. Either way it factors in what you have already saved and the interest your balance earns. It is for anyone saving towards a deposit, a holiday, an emergency fund or any fixed target with a deadline.
How it works
The calculator compounds monthly at rate i = annual% ÷ 12 ÷ 100. Your starting
balance grows to start × (1 + i)^n over n months, and the rest of the goal is
covered by an annuity of deposits.
- Required monthly saving: grow the starting balance, find the remaining gap,
then divide by the annuity factor
((1 + i)^n − 1) ÷ ito get the deposit. - Time to reach the goal: solve
n = ln((goal × i + PMT) ÷ (start × i + PMT)) ÷ ln(1 + i).
If your starting balance plus its growth already covers the goal, the required saving is zero.
Example
Goal 20,000, already saved 2,000, at 3% interest over 36 months. The 2,000 grows to about 2,188, leaving roughly 17,812 to fund. Divided by the annuity factor this needs about 474 per month.
| Goal | Starting | Rate | Months | Required / month |
|---|---|---|---|---|
| 10,000 | 0 | 3% | 24 | 405 |
| 20,000 | 2,000 | 3% | 36 | 474 |
| 5,000 | 1,000 | 0% | 12 | 333 |
All maths runs in your browser, so your savings figures stay private.
What affects your monthly saving the most
Interest rate has a compounding effect over time — it matters little over short horizons (6–12 months) but can significantly reduce required deposits over 3–5 years. At 5% over 5 years versus 0%, the difference in required monthly saving on a 20,000 goal is roughly 60–80 per month.
Your starting balance is the biggest single lever early on. Even a small head start reduces your required deposit because that lump sum earns interest for the full period. For example, a 2,000 head start on a 20,000 goal over 36 months saves you roughly 55 per month compared to starting from zero.
The timeline is the most flexible variable. Stretching from 24 to 36 months drops the required monthly saving on a 10,000 goal by around 120 per month (at 3% interest), at the cost of waiting a year longer.
Practical guidance
- Two modes for two questions. Use “monthly saving” mode when you have a hard deadline (a house deposit closing date, a holiday booked). Use “time to reach” mode when the deadline is flexible and you want to work with what you can actually afford to save.
- Interest rate to enter. Use the gross interest rate your account advertises. For a typical instant-access savings account this is often 3–5%; for a fixed-rate bond it might be higher. If you save in a current account that pays nothing, set it to zero.
- What the calculator does not include. Inflation, tax on interest income, and account fees are not modelled. For short-term goals these omissions are minor; for goals 5+ years away, consider that the real purchasing power of your target may need to be higher.
- Already hitting the goal? If your starting balance has grown to meet your goal before the period ends, the required monthly saving shows as zero. You still need to set a reminder to withdraw or lock in the funds on the target date.
Common mistakes
Forgetting to include money you already have — even modest existing savings meaningfully reduce what you need to set aside each month. And setting the rate to zero when your account does pay interest means you will overshoot the goal and save more than needed.